Bordin, I'd do what I did and get an account created over at 3si.org. There are a TON of knowledgeable people there and they have a bunch more hands-on experience than I have done (so far, at least). As Steve already mentioned, parts are pricey and there are often price differences between a Mitsubishi part that's labeled as one from Dodge, so usually you want to do your price shopping online (DO NOT PURCHASE FROM YOUR LOCAL DODGE DEALERSHIP!!!). I have a program that is very well-known among the 3/S community (CAPS) that makes it very easy to see which parts you can get and what their actual part numbers are. Having this information becomes very useful when you make online purchases 'cause you can shop around for the best prices (my suggestion is to use ONLY Mitsbushi-manufactured parts over cheapos).
As for things to look out for, the timing belts/tensioner/water pump/oil pump (aka 120K service) is vital for these cars, since they have an interference design that will take out valves if the timing belts jump teeth or break. Another thing to look for is spun crank bearings due to insufficient oiling...This is usually caused by a dented oil pan that some other owner just never realizes until it's too late. It's good to see you're looking at a non-turbocharged one 'cause they only add to the headaches of trying to find/diagnose additional problems that can be quite expensive (such as a bad propeller shaft, rear differential, blown VCU, or leaking transfer case).
Another very common issue is valve lash adjuster "tick". Mitsu installed small-bore lash adjusters in all the cars except the third gen 3000GT, so it is quite common to hear them ticking. Most people have been able to correct this non-catastrophic problem with a 3rd Gen. lash adjuster (technically not a lifter) swap, but make sure the proper steps are followed to prep. the adjusters prior to installation. Another thing to check while in this area is the VSS (valve stem seals), since many times people neglect replacing these while they're already in the head. The final thing to check here is the oil cap. It's quite common to have a leaking oil cap, since they are only held on by tabs instead of actually being screwed-into the valve cover. You shouldn't have to worry about this as much as a turbocharged model, but the problem may be there. Mine was mostly fixed by replacing the PCV & I plan on replacing the cap very soon.
The next segment of this saga will be about the ECU/ECM & ECS (if you decide to go with an R/T non-turbo over the ES). As already mentioned, the capacitors Mitsu used in both the ECU and the ECS (electronically-controlled suspension) modules should have never been put into any circuit board 'cause they tend to wear prematurely and leak onto the circuiting, usually taking out traces along their path of destruction.
If you feel confident doing the task of replacing the capacitors yourself, there are kits available that will fix this problem. If you want the comfort of knowing the work is guaranteed from defects & get a lifetime warranty, there are several reputable places you can send your computer modules to be repaired (~$180 for the ECU & ~$140 for the ECS, IIRC).
One thing I also forgot about earlier is window regulators...They are often plagued with a broken plastic tab at the top of the cable mechanism, which causes them to either not work or bind up (eventually leading to a break). I replaced both of mine after having a mishap with my driver's side one on my way home from purchasing the car. I found my replacements through Window Regulators USA on eBay (Alexander) for something like $240-$250 for the pair (after the refund). He fixes them on the side as well, but it was easier to just purchase two reconditioned ones (he adds a reinforcement plate to the plastic so they will never break again) & offers a refund for sending your damaged/broken ones back.
The back-up light switch on the side of the transmission may also be worn out, causing a lack of reverse lights or ones that are constantly stuck on. Fortunately, this is a quick and cheap fix to get working back-up lights again.
The last thing to note are some of the cosmetic eye sores these cars are known to have. The first is cracked defroster vents. It is very rare to see any first gen. ('91-'93) and quite often many others ('94-'96 Stealths/'94-'99 3000GTs) with this problem. In order to fix them, you need to drop the dash & undo some nuts to fix it. The second is a lot of times the door panels develop bubbles between the fiberboard backing and the textured overlay. Another common problem is that the lower window belt molding tends to get cracked/brittle, often causing the stainless underneath the rubber coating to become visible. I swapped mine out with new ones from Rockville Mitsubishi out of Maryland for something like $85-$100 for the pair. The last thing is the leather-equipped cars often have very worn out seat bolsters. They are very nice for being factory seats (have some nice support to them), but they weigh a lot & often are worn. Also, the shift knob and shift boot tend to be tattered, but that can easily be replaced by a new leather-wrapped knob & boot or simply purchase a new boot and peel off the remaining leather from the shift knob to reveal a textured, plastic knob.
If you end up finding one you like, make sure it either has a battery hold-down strap installed or that you install one soon. I have seen too many of these cars without one (mine included upon purchase) and it's cheap insurance (~$25 for the top strap and J-bolt). Good luck with finding one and make sure the current owner(s) have receipts showing proof of workmanship & maintenance records.
I really wish I could have purchased Larry's (Hemi71) old R/T TT 'cause it would have saved me a lot of extra work because mine was previously worked on by some "hack job artist".
Also thought I'd add that I had an issue with water leaking into my rear hatch area by the spoiler's pedestals...I ended up fixing that by making my own seals for each of the three pedestals & RTV'ing them into place. I know several other owners have had similar issues, so it's probably best to be aware of that as well.
And as for Mike's comment, try to find one that isn't Firestorm red (aka "Arrest Me Red") & you should be okay.
If you decide to settle for an ES model, make sure it has the DOHC so you can somewhat enjoy the extra power over the SOHC.
These may seem like a lot of issues, but keep in mind these cars are old now and most of them have been beaten on throughout the years or just took many years of normal wear & tear. As Steve already mentioned, when they're running properly they truly are a blast to drive & you really get the looks from other drivers/pedestrians.
Also thought I should add that the major differences between the R/T & the ES are that the R/T's came with side scoops (on the doors & quarter panels), a more aerodynamic-looking front/rear bumper, R/T taillights, R/T sail panels (that are painted body color), a banana/boomerang spoiler, leather seats (optional) and a blacked-out roof (if still painted as-is from the factory). They also came with only the DOHC non-turbocharged or twin-turbocharged V-6 rated at 222hp & 300hp, respectively. The ES came with a less sportier-looking body kit, optional banana spoiler, ES taillights, ES sail panels (black), cloth seats (leather may have been optional
), and I believe they could have been equipped with either the SOHC or DOHC V-6 rated at 160hp & 222hp, respectively.
