A nice thing to know if you have the export (Chevrolet) model:
If you take out the headunit and replace it by any other model, you do not lose the chimes!
Fist of all, I'm not sure if it's the same in the Us, but in europe all new headunits of really any brand use ISO connectors for power (8 pins) and speakers (also 8 pins).
I did not use a wiring harnas or adapter. I just cut of the original connector and soldered new ISO connectors directly to the wires of the car, so i connected directly to the new stereo (Pioneer AVH-X2600BT). I didn't care to lose the chimes, but when everyting was in place and I turned the key with the door open to try the new radio, the first thing i heard was ping ping ping ping ping ping......
Another thing that might interest you: all over the internet you read about relais or bypasses you need for the parking brake wire. All I did was connect the green parkingbrake wire to ground and my pioneer AVH-X2600BT headunit plays video all the time...
(maybe a difference between us and european pioneer models???)