Hi swinnypga,
Welcome to the Heartland Owners Forum.
One thermostat in your trailer controls the furnace - although I'm not familiar enough with your floor plan to know which. If the air conditioner's blower comes on when you set the thermostat to heat, it's because the FAN MODE is set to HIGH or LOW. Change the FAN MODE to AUTO and that won't happen.
On the water heater, if a Suburban unit, there's a safety switch on the outside of the water heater that protects the unit while on the dealer lot. It's normally left OFF and has a cotterpin keeping it that way so if someone walking through the unit turns the water heater electric switch ON, the heating element doesn't get fired up while the tank is empty. With the outside cover removed, you'll find the switch in the bottom left corner. Note that if you have an Atwood water heater, it won't have this switch.
If the switch is on, it's possible the water heater might have been turned on while the tank was empty, burning out the element. You can investigate further using our owner-written
Water Heater Troubleshooting Guide.