The link above has great info on the mirrors. I have switched all mine out to the newer Gentex models with temp and compass (7 pin connectors). These mirrors can be found in other cars as well, it doesn't have to come from a GP, just go to a local salvage yard and look around. Just make sure to to get the connector with it and swap the terminals as shown. I personally wouldn't go with an Onstar mirror, no need to have a bulkier mirror with useless button on it.