Welcome to AVS! The first advice I'd give you is to read as many of the build threads as you can. There are pearls of wisdom in many of them, often from industry experts.
As for your two questions:
1. Wiring diagram. I don't have a full wiring diagram (actually I'm not sure what you are looking for) but basically there is the electrical wiring, the AV wiring (speaker, HDMI, etc), the control wiring (CAT5, IR, etc). I do have a "design" for the electrical...