Sorry to hear about the change of circumstances, but I'm sure you'll figure it out! Ask lots of questions. Regarding winter storage...
I'd try to find out if there are any leaks
. If you get a good raIn that's the time to look. Checks windows
and vents, but also check the floor inside cabinets- water can run down the walls. Deal with any leaks you find (do NOT use silicone-based caulk), or cover it for the winter. If you do tarp, do what you can to protect the fiberglass from chafing.
Not sure what kind of plumbing your trailer has, but you'll need to make sure it is winterized.
In your climate, I'd remove cushions and curtains for winter storage and use dessicating crystals to keep down the humidity inside the trailer.
If you get much snow, it's a good idea to support the roof from inside. Two squares of plywood with a 2x6 wedged between them works. It's also a good practice to remove snow accumulation during/after storms.
I like to store mine with the wheels off the ground. I raise each side and put a jack stand on the frame behind the axle
. I also place stabilizer jacks at the corners. Mine has a rounded roof, so I store mine level, but if yours has a flat roof, dipping the tongue will aid drainage.
Most important, check the trailer from time to time throughout the winter. The sooner you catch any issues, the less harm done.