This is out of my van thread.... Get these books and you will be well on your way.
I have done a lot of wiring before so I am very comfortable doing it. I know a lot of people are intimidated by the "spaghetti"... If you want to learn more I would suggest picking up two books. Both of them are by Tony Candela and are very well written.
He touches base on all of the basics in his first book

and covers some fairly in-depth projects in his second.

I have read through both of them a few times and everything I am doing here on the van I have either picked up through Tony's books or had my knowledge reinforced or changed for the better by him. The other thing I can tell you is, if you want to learn to do your own wiring, get out and do it. It's not that difficult and, with these books as reference, I think anybody could re-wire a car with little difficulty. Or just start small by tiding up all of those loose wires!
Thanks for looking
Mark