I work for a nissan dealer. Only the nissan cars have CVT. All of the trucks have a 5 speed tranny. The Xterra should be able to handle the snow machine and trailer just fine. We have plenty of people up here that do just that with them. The 4.0 is the same motor as the Pathfinder and Frontier as well. The only issues you might have, and I will list them for you.
All rubber tranny cooler line will start leaking. Front diff pinion seal and axle seals will start leaking. If the axle pops out of the diff in the front, then it's time for a new diff. Trying to just pop it back in won't fix it. It will just pop back out. Power-steering line with sensor will start leaking. Both rear axle seals will start leaking. And for the grand finally, The timing chains on all 4.0's usually go bad before they should.
Now this doesn't mean they are junk. Or that they will all go bad at once or in the near future. But those are the most common things I see that come up on them. Oh, I almost forgot. If you find that your tranny fluid is milky or that you have tranny fluid in your coolant tank. Start saving for a new radiator and more than likely a new tranny. If you need to know anything else, just ask.