I came across this towing chart for 2013 Ram 2500`s-here is the link
http://blogs.cars.com/files/8-ram-2500-hd-towing-2013_01-08-13.pdf
According to this chart his truck can tow a trailer in the 16,500-17,000 territory. As other people have said the GAWR of the rear axle will probably be
the limiting factor. Saying that, they show the base weight of the rear axle in the 2700-2800 pound area and the GAWR of the rear tires at 6200 pounds and the GVWR at 10,000 pounds. They also show the total basee weight at 7000-7200 pounds.
So say the base comes in a little higher and when loaded with fuel and ready to go camping the 7700-7800 and say the rear axle is 250 pounds heavier.
So with the real axle weighing in at 3100 pounds he has still got 3100 pounds left for pin weight. Yes he will be over the GVWR but he will be right at his GAWR of the rear axle.
So he may well be able to tow this trailer. He will be over GVWR but most people tend to agree that this number doesn`t hold much water and that you really need to make sure you are not over the rear axle GAWR.
Now don`t get me wrong, he DOES need to go weight his truck full of fuel and ready to go to see where he is at with his weights and also come up with a educated guess on the pin weight but he might be very close to being in specs except for the GVWR.