Excellent choice of welders, I have a Autoset 212, 120 and Diverson (TIG) and love them.
what you are contemplating isnt that hard, you just need to take it slow and think about what you are doing. Of course it would be much better if you had someone local you could talk to and who could oversee what you are doing, but you can do it. The biggest issue is getting over the fear of doing it. Some helpful tips
1. you need to be a little cautious with heat. When you first start welding you think of like what you have seen where someone is laying a continuous bead on a piece of metal. With sheet metal (as on a car) this will lead to more problems with warping, burn through, etc. Watch a lot of you tube videos, car shows, etc and you will get the idea.
2. one of the harder things to get your mind around is tip distance from the weld. People tend to want to be way too close or way too far from the surface. You need to be in the shield zone so your gas (I am assuming you are going to be using Argon verses flux core wire) can shield your weld.
3. do not expect your welds to be "pretty" like on TV. First off these guys have been doing this for years, secondly you have no idea how many takes it took to get the footage they show.
4. if you start burning through (this is where when you start welding the metal melts away and leaves you with a hole); stop what you are doing and look at your settings. Just because the car was originally made with 18 or 20 gauge doesnt mean that metal is still that thick. Turn down the heat and try again somewhere else.
5. when stitch welding (making small welds one after another), it is helpful to start your weld slightly on top of the last one, however do not be too quick or it will melt away leaving you with a big hole (see #4).
6. do not be in a hurry, let the metal cool some between welds. In some cases you can use an air hose to help cool it or even a wet rag/sponge.
7. make sure the metal you are going to weld in is EXACTLY where you want it when you begin. There is a whole art form to shaping and positioning the piece. Sometimes you need to be creative in how you position and hold the new piece.
8. You cannot weld rust with any degree of structural integrety. What I mean is you MUST cut out the rust, how much depends on how much is there. General rule of thumb is at least 1" into good metal past the rust on all sides.
9. dont be afraid to grind down your welds as you go, but do not get too aggressive with your grinding or you will just make it thin and cause more problems than you already have.
10. understand that when you weld two pieces of metal together, it will most likely not end up looking like just one piece (like you didnt weld one peice to another); it can happen but more times than not you will be able to see where yo welded them together and have to do some body work to complete the repair. The 2 peices need to be in near perfect alignment and your grinding technique needs to be good.
There is of course tons more on welding and others can chime as they feel necessary, however I strongly urge you to practice, watch some videos and look at some books before you just straight in. That said, do not procrastenate forever, jump into the water and begin to swim. Just remember, in general, you can fix anything you do wrong, just know when to stop and seek help.
