Questions about a 1995 Fleetwood Rio Grande

Remember on the Battery hookup, white wire is the ground wire on DC circuits..If hook up backwards can cause a big problem. as far as HW heater look for a door with louvers on the outside, should have a round tab with a hole in it, this is the door to the HW heater.
another good site for you is www.popupportal.com, this is dtrictly pup's and someone on there will have a unit like your Son's.