I am happy to pay $15 and most likely will just order them, but I am most concerned with the wiring that goes to the Onstar module. As long as we can isolate the following wires on the onstar module, I am sure I can get the bluetooth system integrated in. The next step (and more difficult) would be to get the spec for the HUD and be able to display the phonebook on the HUD display or something.
For Audio I would need the following
telephone on (?) tells the radio to play telephone signal
telephone mute: Mutes radio
maybe a communication bus to setup some type of translator to show the phone info on the radio or hud
Connection to a voice button to activate voice recognition and pair the phone. (worst case another button somewhere)
Here is the system I would use as a model
Voice control guide