Just bought our first trailer, 2011 25DS and we are clueless

. I have the trailer connected to electric, backyard. We are in South Carolina and have trips planned through the winter. I plan to use a small electric heater inside, for when the temperatures dip. Our coldest, weaterh, Jan. & Feb. can get into the teens at night. Am I covered with the small heater and the hotwater heater getting electric or do I need to drain the tank after each trip? Anything else outside that can freeze?
Our two hour dealer walk thru is now a blur. Where is the switch for electric only to the hot water heater? Inside the trailer or at the tank itself?
By tripping the hot water tank breaker, does that keep both propane and electric from turning on?
Our maiden voyage will be Thanksgiving...any other tips or guidiance would be greatly appreciated.