The drive tires of the TV are the only tires that need chains ore Blizzaks. The 5th wheel does not use chains or Blizzaks. As far as driving a diesel it's about the same as a gasser. Your dealer can fill you in on any special details. Operating the 4 wheel drive is either turning the hubs on the front axles or a dial inside the cab. Again, your dealer can fill you in on those details.
There is nothing better than gaining experience in towing the 5th wheeler. The more you tow the better you will get. Practice before you leave if you can. There are videos on the web to help explain the important facts about towing a 5th wheel.
There are also links on how to maintain you RV and how to operate it.
A rookie towing in snow could be dangerous. Like someone stated plan you route and look for campgrounds where you can wait out a storm or dangerous weather.
This is a great site for advice. Use it and I'm sure you will do well.
Best of luck to you and your wife.