[hotbug1776]

From what I understand (after searching the Org for the info), if you remove the stock stereo, you will lose your onstar, and vehicle warning chimes. the solution is to mount the stock unit in the rear (trunk) and use a t-harness to retain the two affected items. there is also a module you can get to replace the chimes/onstar, but it's cheaper to just move the stock deck i believe. check at best buy/circuit city for the harness.