I haven't read this one but it sounds like what you are looking for.
"Gunsmithing At Home" by John Traister
I'm assuming from the tone of your post that you don't have a mechanical background. This may be why no one responded earlier.
Minor repairs aren't rocket science but there are some basic skills that you will need to develope. It's a hands on kind of learning. If I were to make a suggestion it would be to get a couple of cheap beat-up guns and make them better. If you screw up, and we all did(and do), at least it won't be on grandpa's favorite deer rifle.