Ideal MIG welder set up for body work... What to use? What works best? HELP!

Go with the gas and smaller dia. wire. Be sure to make some test/practice welds on similiar gauge scrap metal before you start on expensive or non-replaceable quarters or fenders. When welding vertically, start at the top and work down. Don't try to make one continuos bead, you'll warp the panel. Make a bunch of "stitch" welds or even perforate the panel and "rosette" weld the panles on after flanging it. Get used to the weld, grind, weld, grind routine! LOL!

Good luck!