I have the 2007.5 Chevy version of the truck you are looking at, 4x4 extended cab long bed with 4.10 rear. I've put 50k on mine and am very happy with it. I tow rather frequently and I am impressed with the drive train. I feel it has ample power for what you intend on using it for. You will know the trailer is back there more than you do with your PSD, but the 6.0 gas has plenty of grunt to get the job done. I came from a 7.3 PSD with 3.73.
I tow my deckover bumper-pull at 7-12k on a fairly regular basis and get 10-11 mpg on average at 55-60 mph. Enclosed trailers run as low as 7-8 when it is windy and -20 to -30 F, and up into that 11 range in the summer. Running empty with my 10 mile commute I average 12.5-13, and longer empty trips I can get 17+ at 55, and 15 at 75.