The only real decision for the welding you'll do on a Jeep is 110 vs 220. You simply want to go MIG (wire with gas) if you just want to get down to joining pieces of steel together. You can't go wrong with Hobart, lincoln, or Miller. Hobart even uses a Miller gun. Think of Miller as a more expensive version of Lincoln, but one that's still built to last if it's not used in production every day.
Stick is more versitile and cheaper to buy, but much more difficult. I ended up with a Hobart 220 mig about 6 years ago and couldn't be happier with it. It's been used for things I never imagined. 110 is more convenient, but 220 came in very handy when building trusses over axles and things that required welding thicker metal.
EDIT: just caught up on the thread: that'll do!