Tanks for the quick replies!
i have not installed a car stereo before but i am an electrical engineer, at least will be very soon

, so i thought it might not be that bad. If i get in trouble at any time there is an installer close by.
I have the factory monsoon 6 disc changer with xm, amp and subwoofer. I will be keeping everything the same back there and will just be changing the head unit. Is the install any diffrent with this set up than with what you guys were describing above or are you right on?
Do you guys know how the output on the z1 can be connected to the headrest dvds that were in the h3 promotion, so that if a dvd is played on the z1 it can be viewed on the headrest dvds?
Where would be the best place to order the onstar interface and the chime one, and the wiring harness and what ever else may be required for the install?
Oh and some pics would be great if you have some.
Thanks again for your help guys and i apologize for all the questions!