Get the Haynes book in hard copy, and just keep a copy in your 914. You will thank me for this later. I have 2 copies. The greasy one I use in the garage, and the nicer one I keep in the house.
Make a color printout of the 914 electrical system. It will prove invaluable. You can find it on this site. I glued mine to a BIG posterboard and hung it in the garage.
Tech Tips 700 is a good reference.
How to Keep your Volkswagon Alive is another good reference. Its also just fun to read, though it is more T1 specific, it does have chapters on the T4. But its more about the zen of aircooled ownership and very detailed engine building.
Zach