Barnett's Manual is a good place to start. Lots of reading, but you don't have to read every word. Just do it on an "as-need" basis. It's not quite the bible. Sheldon Brown's site at harriscyclery is good, along with the Park Tools site for referencing some of the more common problems. Barnett's tends to overdo the line drawings rather than show perspectives in photographic form, which the other sites do. It still can be confusing.
Don't worry, even the pros started somewhere, and that usually meant working on their own bikes, making a few mistakes and learning by them. Probably a couple of things to remember:
1. When disassembling something, use either a twist-tie to retain the parts (eg, cogs) in the order and direction they come apart, or make up a simple drawing as you dismantle. I'm am not well-disciplined in this area.
2. You *will* end up with a bit left over if there are more than five pieces to assemble. Don't worry. Just dismantle and start again. It's good practice and will take you half the time to do again!
3. Lubricate most threads with grease (to avoid corroding together). Exceptions are bottom bracket threads if you believe most advice (use Loctite in the blue variety).
4. Don't overtighten. Snug it down. Barnett's has good detail on torque settings. If you do enough of your own work, you can "feel" the torque automatically on your hands.
5. Don't force anything. If it isn't working as it should, there is a reason. Investigate why.
6. Undo anything with ball bearings in it over a bowl, plate, table with battens around it... anything to stop those pesky little things disappearing forever into carpet pile or some distant corner of the room.
7. Enjoy the challenges. The more you learn, the more self-reliant (and creative) you become!