Looking for the Telematics/OnStar install location

I recently purchased a 2002 Tahoe Z71 with OnStar, as the unit is now out of date, I would like to use the antenna, control module and other items in other ways. I just want to know where the module is located so that I can find it and modify what I need.
I used to work on the design team that produced those Telematics Modules, and would rather play/hack it then upgrade it to digital. But I would like to know where the module is located before I tear apart the interior of my new, to me, vehicle.
All HELP is very much appreciated. Thanx!