An RV can be divided into basically 3 parts for this disucssion
Engine-Chassis-Drive train.. Many sources for manuals Chliton's for example. it is basicaly a GM chassis even if it's a workhorse custom chassis.
"Stuff" (Tv's. water pump, Furnace, Fridge, Doors, Mirrors, Windows, Air comnditioenrs, Fans, most every thign bolted to your RV) Download the owner's manual from the device manufacturer.. Google Make Model Manual (Replace make and model with the make and model number)
Finally the wiring diagrams.. No joy there at all. you are on your own, Same for plumbinmg but there are a few miles less to figure out.
HINT. IF at one wall the baseboard is a "Riser" like thing (Single step) That is where the utilities run (Water, Sewer and Electric may all be in that riser)