My personal experiance with the OEM camera install is when I tied in the power to the reverse lights, every time I hit the brakes, the picture flashes once. I assume from the drain on that circuit. But I did tie into the ground and the power wires on the reverse light. I was wondering if there was a closer switched power source myself

 

If you put a cap on that circuit, that should fix the quick drain of that circuit.

 

Tap into the hot lead for the rear hatch light on hte upper right side of the hatch.

 

GM geeks are right. behind the rf kick, there is a 3 wire connector in behind another connector. pink, blue and a bare wire. connect an RCA lead to the pink and blue.
as far as power and ground, use the wires coming from the reverse light. its not hot or accy....but why do you need it? the camera only needs to be on when it is in reverse. connecting it to hot could cause a drain on the battery, Accy would cause the cam to be on the entrie time the key is on, thus reducing the life span on the camera.