Bottom Door Rust Repair Help

[msbaugh]

Well this isn't for my Challenger, but it is a Mopar truck.  I've seen a lot of good body guys here so wanted to ask for help here. 
The 2 first pictures: bottom, inside of the door (where the outer door skin folds over the inner door skin).  This lap has collected moisture and developed two rust spots. 
The third picture: view of the same spots, but from the top down and inside of the door.  The rust so far has not spread to the inside, but I want to grind all of the rust away to keep it from spreading. 

How should I cut the folded over part out to get to the inside and start the work?

I am not a body guy but wanted to learn, this is a spare door for my Cummins truck.  I can weld very well but am new to body work... want this to last as long as possible.

[GoodysGotaCuda]

Your pictures don't seem to be showing up from photobucket.

[msbaugh]

Photobucket apparently has stopped sharing my photos with 3rd party sites unless I pay a $399.00 premium!!! Well... there goes 5 years of my pictures on this forum... oh well...

Can you see them now?  BTW Goody, got your box, thanks a lot buddy!

[jimynick]

You're in the early stages and there doesn't appear to be any perforation yet. If the seam is swollen, I'd use a body hammer and dolly to whack it flat again. This'll pop the rust loose and if it's about to go through, it'll likely do it then. If it isn't swollen or perforated, I'd sand/media blast the area clean. You could pour a wee bit of rust converter inside in that area and then I'd sock the Krown rustproofing to it and you should be pretty good. Reseal it and paint it with an epoxy primer under it. It's one of those gray areas where welding may not be req'd. The welding alternative is much more labour intensive. Just my 

[msbaugh]

Can you guys see my pictures now?  The fold over on the bottom is worse in a couple spots than I thought it would be.  I opted to cut off portions, not completely separating the skins and to grind out all of the rust.  My first thought is to treat it with por15 or something as is or epoxy primer and paint. 

What tools would I need to make the fold over in the sheet metal if I were to cut from the front and weld in a whole outer skin patch? Would that be the better route to take?

[jimynick]

I wouldn't have done that, but since you have....you'll think I'm crazy, but I'd now clean those lips and if they're not perforated, I'd bond them back on after having cleaned and epoxy primed the shell and strips. Unless you're very good with a welder, trying to weld replacements into the bottom will warp the outer skin and make an even bigger mess. Again, just my 

[msbaugh]

I wouldn't have done that, but since you have....you'll think I'm crazy, but I'd now clean those lips and if they're not perforated, I'd bond them back on after having cleaned and epoxy primed the shell and strips. Unless you're very good with a welder, trying to weld replacements into the bottom will warp the outer skin and make an even bigger mess. Again, just my 

I do think you're crazy!! Is welding in a lower, outer door skin that hard?? that bottom lip is rusted all in between that fold.  They salt the roads like crazy here, I really want to make it bullet proof, I feel like leaving it as is would only mean rust a year or two down the road.  I ordered a pre-made door skin from LMC truck that's supposed to fit really well and already has the fold on the bottom at 90 degrees.  This is a spare door, so if I screw it up, I'm only out $100 and stuck with 2 rusted doors

[jimynick]

As I've said many times before- your car, your rules. I'll wish you good luck with your door skin and have a good day, sir.

[msbaugh]

Not trying to be rude buddy! I appreciate your response, just trying to weigh the alternatives and make the best repair possible.