I believe I would either do a full restoration on the tractor of leave it like it is. Since you are asking about body work I get the impression you would rather fix the tractor up nice. There are a few autopaint guys here that would be more than happy to walk you through the project if you choose to do it. I have done enough auto painting I could help you also. I can also give you the site address of a auto paint forum that has several autobody guys that would help you.
Whatever the type of work you do on the tractor, be sure to thoroughly clean the oil and grease off the tractor. The slightest memory of oil will have the paint pealing off so I would spend days just cutting the oil before anything was done. Some places will take oven cleaner to cut it. Purple power is a good product and I also use Krud Cutter Gloss Off from Sherwin Williams and a power washer.