It's difficult to tell from the picture, but if there are some rusty spots and chipped paint, you will likely have to clean them real well and at least spray some paint on those areas. If you're going to do that, why not just clean the entire tractor and paint the whole thing? It'll be ready for the Fourth of July parade then. You can impress all of your neighbors, too.
Whatever you decide to do, enjoy your old tractor. I love my collection and ride them just about every day.