There's a good book on guitar repair by Hideo Kamimoto. The Irving Sloane book is good, but is a bit restricted.

If you need to repair cracks, there are two techniques - fill the cracks with filler, or fill the cracks with wood. Personally, I think filler is for idiots, but it works if you apply a solid finish over the top - many repairmen would use this and refinish the guitar in black - very common for archtops - if you're not confident of your abilities, this is the safest option, as it can be dug out and replaced with wood at a later date. I once dug out a bad crack filled with filler on a Gibson Heritage and replaced it with wood. I sold it to a friend, who went bankrupt. The guitar was auctioned and sold to another repairman. I walked into his shop and found the guitar - he couldn't tell it had been repaired at all until I pointed to where the knife slipped and I left a tiny bloodstain. So don't be afraid to try filler as a make it work fix until you have the skill to use wood.