Man, I can tell I have gone thru too many jobs. A LONG time ago I worked at the Firestone at Walnut Hill and MacArthur. Also I worked at a Buick/Pontiac/GMC dealership in Grapevine down the street from that other Firestone (Freeman).
As far as it paying 2.1, was that warranty time? Its been a while since Ive worked on them but that seems low. I have also never done one on a Colorado but I am assuming you still have to drop the tank or remove the bed?
I know its different on cars, but at a freightliner dealer I work at its 105.00 an hour, parts, shop supplies(15% of labor cost) and taxes on parts and shop supplies. I know the car dealer I was at the labor rate was a tick higher.