Audio Systems: 2 questions about car stereos please help, car stereos, van conversion

Question
the first question is i just got a 1994 gmc 2500 van conversion???? it has blinds inside but anyways, somebody cut the factory radio harness off and i need to know which wires control what.... or where i can get a wiring diagram,
2nd question is i have a 97 vw golf i took it to a mechanic and he put a new ignition in the car and never did get the radio workin right afterwards, thats taken care of but i dont know how to input my stereo code, please tell me how to do this simple procedure thank u very much, and please help me.
                                         thanks,
                                               josh

Answer
gm wiring

http://www.installdr.com/Harnesses/GM-Wiring.pdf

about the Volkswagen you need to unplug the battery over night the next day it will display code
wait for zeros and input the code 1 number at the time using the radio 1 to 6 buttons