The deal was the employee pricing GM had going for awhile. Now it's the Red Tag event. No negotiating involved.
The following example is from GM's website:
2008 Chevrolet Tahoe SUV 2WD LS with option LMG 5.3L V8
$36330 Base MSRP
$33785 Red Tag MSRP
-$1000 Lease to Purchase Cash
-$1500 GM Special Cash
-$5000 Customer Cash
$26285 Your Price After Applicable Offers
(Offer on models in inventory as of 05-09-2008 while supplies last).
Go see a dealer. I'm sure they'll be pretty straight with you to unload a Tahoe.