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You might have to run the Vehicle speed sensor wire over from the connector in the right kick panel, IF it is not in the radio connector. They were supposed to remove it from the radio connector unless the vehicle has NAV from the factory. So, it might or might not be there, but if you have to run the wire, that is only about 20 minutes; max.
You will have to have a dealer reprogram the radio to the GM internal LAN. Not sure on cost, but about ten minutes max by a tech with the Tech 2.
The NAV antenna can be mounted just above the center heater ducts, just above where the radio moutns. That's where I mounted my Pioneer GPS and it works fine.