I am a 29 yr old female and I installed the Bluestar II yesterday in my 2006 Envoy by myself. It was easy!!!!
It took me kind of a long time to find where the OnStar Module was located, so I just want to post to help anyone else. It was not behind the glove box, nor was it under the first row backseat on the driver's side (I was convinced I found it both times). Then I checked the back of the truck and thought it would be in with the car jack, but it wasn't.
For the 2006 Envoy it is behind the passenger side first row backseat, under the plastic cover.
Once I found it, it literally took 5 minutes to hook it up and connect. Easy! I've made about 6 phone calls to test it out both parked and while driving and it is working perfectly with my iPhone 4s.
I have not figured out how to use my iTunes with it, and I'm not sure if that's even possible. But I really just wanted it for the phone calls anyway. Excellent product so far.