OK, I was in the same situation as you about 8 months ago. First of all, you are doing the right thing (IMO) by buying the 5er before the truck. I bought a 37' Cedar Creek with optional heavy duty running gear - GVWR is 15,500. I believe your Montana will be almost the same. When I'm loaded for a month-long trip, I weigh about 14,500 or so and have about a 3,000 pound pin weight.
I agonized over what size and type truck to get for quite awhile before and during my 5er purchase. Did lots of research on towing weight restrictions on trucks. Almost everyone on this site suggested that I would want at least a 1-ton diesel 4X4 with almost no agreement on truck make. But the concensus was that any of the big three HD pickups would do. SRW or DRW was always a question that was difficult to get agreement on. In the long run, the DRW won out for me. I got the truck in my sig and have been VERY happy with it! BTW, I would probably have been happy with a Ford or a Ram too. But I got the Chevy. The dually seems to give lots of lateral stability while towing and when you are experiencing strong crosswinds, that is important.
Both my wife and I have no trouble driving and handling the bigger truck, either while towing or solo. Took a very short time to get used to it but after that, a breeze! Backing is still a bit of an issue, especially backing toward my "blind" side. But we work together on it and manage to git 'r done - and we are improving.
Good luck and enjoy that 5er!
