I bought my '12 Denali in January just for towing a brand new 4400 lb dry weight travel trailer. I returned last week from a 2500 mile maiden voyage. Some random thoughts and things I have learned:
Your loaded weight of the TT will be a lot more than you estimate.
Don't exceed TT loaded weight by 90% of your towing capacity for safety's sake.
Look up TT weighing procedures online and follow them at a commercial truck stop scale. Yes, you have to pay to get weighed, just like with women.
If you buy a used TT buy a new weight distribution hitch and have anti-sway attachment points installed on the trailer tongue. Install an anti-sway bar.
If you buy a used TT check the date of manufacture of the trailer tires. Odds are they have aged out and need replacement regardless of tread wear.
If you buy a new trailer from Camping World *SPIT* or other provider be sure to make them print the owner's manuals (available online only) for the trailer brake comtroller and weight distribution hitch. And then check if any of the interior equipment installed in the TT is missing "online only" manuals and make them print those, too.
At Camping World *SPIT* I had neither the weight distribution hitch manual nor the trailer brake controller manual when I started out on my trip and they also failed to mention that the weight distribution hitch has to be adjusted according to the manual AFTER you load up the trailer. They did tell me how to adjust the trailer brake controller, sort of.
I don't care what other people say, air up your rear tires by 4-6 pounds.
Check the air and oil daily while towing.
Unless coasting a long, easy downhill slope on the freeway, keep the vehicle in tow/haul mode. I thought I could get away without it on I-95 in pancake flat Florida but after a few minutes of the transmission hunting for the right gear every fifteen seconds, I relented and kept it in tow/haul mode.
I plan to get a tune to defeat AFM and to improve transmission shifting and add a few ft-lbs of torque. But I also plan to drive the US and Canadian Rockies as well as Alaska in due time.
I also plan to buy an aftermarked transmission cooler due to the above.
But I'm not saying you have to have those two things.
Hope that helps.