It's a total of 2600 which includes the stand alone Pontiac dealers (39), Saturn (400), Hummer(?) and Saab (200) dealers. The other 2000 or so will be mostly metropolitan GM dealers (mostly Chevrolet). The small town dealers are said to be safe. Some of the 2000 of course are multi-line dealers that will remain open to sell their other brands. This number will be achieved by October 2010 when all dealer franchise agreements expire.
When a dealership closes the nearest dealer is assigned the customers from the closing dealer for sales and service.