My gut feel is that it will cost you more to have a shop do your bodywork right than what the truck is worth, before or after the work is done. Rust removal, done right, can be a very time consuming process. If it looks rusty from the outside, chances are high that there is even more rust once you get into it. I usually buy rusty vehicles real cheap and then spend a ton of time removing the rust. But that is what I like to do. If you do not like doing the work, you may be better off finding another truck that is more solid.