Most of the wiring and plumbing is so simple there is no great need for diagrams.
AC wiring runs the air conditioner, the microwave, some outlets, maybe the hot water tank and the converter that charges the battery.
The battery runs the lights, the water pump, the furnace fan, the circuit boards in the fridge and hot water heater, the bathroom fan and maybe an inverter for AC power off grid.
A lot of the wiring runs from the fuse box up to the ceiling and across the top. Google RV roof repair and you'll see how it's done on a video where somone has removed their roof to repair it.
Propane runs the hot water heater, the furnace, the stove and the refrigerator.
There is a clean water tank that will hold around 40 gallons and is pumped to the sinks, showers and toilet with the 12VDC pump. The hot water heater will provide heated water on demand if it's been turned on and/or lit. There will also be a connection outside for "city water" that connects to the plumbing system "after" the pump and will supply everything without filling the tank or running the pump. There will be a second outside connection to fill the tank. Some units have one connection and a "diverter valve" to direct the water where you ant it to go.
Most of the plumbing is "inside" the trailer, it's at the back of the cabinets and behind the sinks and under the fridge and stove. This keeps it from freezing as long as you run the furnace when you're camping in cold weather. I replaced all of my pipes and they were all accessible inside the unit.
Water from the sinks and shower go to the grey tank, Toilet flushes go to the black tank.
