If you're getting this from a dealership try to make them replace all 4 window regulators as a condition of the purchase. Or if they won't, have them knock off $600-$800 dollars (because they will probably go bad)
I have an 02 as well (but no SC)and love the truck (aside from the aforementioned regulators)
Also, $12k seems kinda high to me for an '02 with 75k on it...but I didn't KBB the price to check. I'm sure you've done that.