My Nakamichi CD-400 just arrived....I followed the instructions on bmwe34.net to try and install the head unit myself, although I'm at a stopping point. I bought the BMW Wiring Harness from Circuit City, but they don't have a "universal harness" that will connect to from the BMW harness that I purchased, to the Nakamichi. The harness that came with the Nakamichi is all split up at the other end....how do I know which wires go to which on the end of the BMW harness?