Replace your warm weather oil with a more suitable 5W-30 oil for winter time use in the truck camper's engine.
Switch over to studded tires if possible. If not, keep a full set of winter tire chains in the camper. Put the chains on when traveling on icy or mountain roads during the winter. Check for road signs telling you to chain up in the required areas. Pull over and place the chains onto the tires to continue the trip.
Drain all sinks and holding tanks and add a half cup of anti-freeze into the drains in sinks or showers. Pour two to three gallons of anti-freeze into the gray and black water holding tanks.
Drain the fresh water tank if you do not have a heat source at the tank to prevent freeze up. Use water jugs and store them in the heated camper cabin during winter use.
Apply the heat film over the camper windows and blow the hair dryer on it to set it. This prevents heat hemorrhage from the windows.
Bundle up with plenty of sleeping bags and blankets at night.
