The biggest thing with rust is you have to cut (or grind) out the old rusted metal, and weld new metal in to do it "right", there are a lot of band-aid type fixes, but new metal is the only correct way to go to keep it from coming back. Body work is very time consuming, esp if you don't have all the air tools to work with and are doing it all by hand. It's not impossible mind you, but just be prepared to take your time with it.
Like Zukipilot said, a lot of body shops won't take amateur body work, but if this is just a trail rig, I love the look of primer, or you could just carry it to one of those cheap places..macco or there is another I think. They will scuff and spray paint on almost anything you want really cheap. Not the greatest work, but if you do your sanding and prep work before you take it there it can turn out ok from what I have heard.
If you want to try it, I say go for it, just realize that it will take awhile, and you truck will be spotted with primer for quite awhile while you work on it if you don't have something else to drive.