looking online at the max tow rating for that year/model:
Yukon XL 1500 2WD 8,100
Yukon XL 1500 4WD 8,000
Yukon XL 2500 2WD 9,600
Yukon XL 2500 4WD 9,400
so depending on which one you have, these are the max tow limits for that vehicle.
Next - payload, This really should be pulled from the sticker inside your vehicle. the yellow one that says something like "The total weight of cargo, people, etc in this vehicle should not exceed xxx lbs"
couldn't find the payload info on line for that make/model year.. but just based on the tow capacity, I'd guess you're trailer is too big for the vehicle..
unless you have the 2500 version - then you might be ok - with tow limit weights at least. But with Cargo - that's the big question. if you don't have the payload requirements you won't be able to tow it..
Good Luck!