I've heard of a guy on youtube with some colorful language who has some videos on airhead maintenance. I can't recall his name, but hopefully someone whose referenced him will chime in.
If you haven't checked out
www.bmwmotorcycletech.info you should. Not a lot in the way of pictures, but full of useful information. Run by the man, the myth, and the legend "Snowbum."
Also, there is a book (with pictures) called "Classic Boxer Charging (Version 2) by Rick Jones, owner and operator of Motorrad Elektrik www.motoelekt.com that explains the electrical side of things.