Well, since you already bought it... What is any of us going to say to change that?
You got what you got. If the dealership sold you that trailer knowing what you had for a vehicle and still said "you'll be fine", then I guess it's hitch it up and see what you think..
My guess is that unless it's a 3500 dually, it'll be a pretty heavy load..
My Dad has a 5th wheel that has a #15,000 GVWR (the most it can weigh all loaded up) and he has a 3500 Dodge Ram dually and he does fine, but it's also under it's ratings on both the truck and the rear axle.
Good luck!
Mitch