I have a 2012 2500HD diesel and I wouldn't hesitate to tow that with my truck, but I would use a good WDH for ride comfort, and replace the factory shocks with Bilstein if they are over 3 years old. The factory GM shocks last about as long as a set of tires.
I tow a 6k trailer with mine and it really doesn't break a sweat, but I do use a wdh to keep it from porpoising over rough roads.
I thought I wanted a 5th wheel but with 2 kids and 2 dogs the bed space on the truck gets used up.
Factory tow rating for bumper pull on a crew cab 2500HD with a Duramax is around 13500 lbs.
