Any good service shop can change out the diff fluid and transfer Case Fluid for less then $180.00..!!! Look up in your manual for the type fluid recommended By GM ..so when you go to the shop you'll know what's supposed to bee in there.
I would let a dealer drain and service your Auto Tranny. This way...If their's a screw up it's on them. Also..look in the manual for the milage service point on the tranny.
$170.00 sounds a tad high for the tranny... But at a dealer rate of $100.00 an hour it could be about that. I would shop around for other GM dealers for a price. Doesn't necessarily have to be a HUMMER dealer.
Your driving a Mod-ed Chevy Colorodo Truck...It should be able to be serviced at any GM dealership. That tranny is used in other GM rigs.
Some dealers have specials on service..Shop around
