OK, Finally reporting back to anyone who is still following this.
I finally got it wired into my factory sound system. I used a Cellsite GMCSS-2 harness from electronics outfitters.com (part is about 30 bucks) I tried originally to just direct wire it but the problem seems to be that the mute function will not work without the adapter kit.
I plugged in the harness (between the radio and factory connections) and rewired the IHF-1000 power/ground/switched leads onto the harness and it worked perfectly.
Best part is I still retain the onstar functions, and can adjust the IHF-1000 volume from my steering wheel controls for the radio. When a call comes in or I activate the IHF-1000 the radio display will say "PHONE"
here is a link for the cable I used.
http://www.electronicsoutfitter.com/store/GMCSS-2