I would enrol on a welding course at college. That's what I did and the tips I learnt were excellent. Welding car body work can be very tricky due to the very thin metal in certain areas. I'd practice on some gash panels first.

I'd buy a decent MIG welder (forget about a gas less one) and a decent compressor if you want to run air tools for cutting etc.

I'm no expert by any means but I can state it is a lot harder than it looks to get even a decent job. Good luck!