Location of the limit switch for a surburban nt30sp in a Keystone raptor

One way to locate the water pump is to turn on a facet and then turn on the water pump. You should be able to hear it run as it tries to "catch up" on water flow/pressure. Look where the sound comes from. You can find the water heater from outside the RV by looking at the walls for a access door that has a screen on a portion of it. This will be the location of either the water pump or the furnace. If furnace, look for another such door.

While not familiar with that particular model, it will be easy to locate. Just turn it on and listen. It WILL make some noise.

Some are accessed from an outside panel, under a bed or cabinet, thru an access panel inside, outside or a storage compartment outside.

If the under belly is a black plastic cardboard type material, there should be a series of self tapping hex head screws along each side that you can remove until you get enough slack to gain access to the valve. Or - you can use a razor knife and cut a square access point there the valve is located. Once the valve has been replaced, to reinstall the access cover, puncture a hole in the main portion of the underbelly and adjacent to that hole in the cover make another hole. Do this a couple of times on each side then insert a zip tie through opposing holes and secure. If the valve is hard to get into place you can use thin metal flashing and Vaseline to help with the installation. Take two thin pieces of flashing, rub Vaseline on both sides, place the new valve between the to pieces of flashing like a sandwich. Then slide the flashing and valves between the hub fittings. Once in place slide out one piece of flashing at a time making sure the seal properly seats. Then slide the flanges back into place, if loose, and install the new bolts.

Look for a brown or black square box, usually located close to the floor. The upper portion of the cover should open then you press the upper center. However, I have seen the breaker boxes located in an outside storage compartment close to the shore power connection and also under the bed.

Typically not. I have installed shutoff valves on several, at customers request, to prevent the genset from losing prime.

On some later model Montana 5th wheels, there are actually three holding tanks which will eventually require draining. (two grey tanks, 1 for the kitchen sink(s) and 1 for the bath tub & bathroom sink, and one black tank, obviously the toilet...) The two most used drain valves (1 black & 1 grey) are together in the docking station area where the city water supply is hooked up, the other (kitchen sink) is at the left rear of the coach behind the farthest rear wheel along the frame. (That is where "Keystone" installed the grey tank for the galley, or kitchen if you prefer.)
If certain it is the black tank which won't dump when the black tank valve is pulled, there is a restriction before the valve (or the valve itself is not opening hence a broken cable to the valve?) One might try "snaking" up into the sewer line, measuring the distance from the outlet to the valve location, assuring it is either open or closed. Once that has been determined, you will at that point have to remove the sewer line at the valve for repair. Be sure to wear latex gloves and eye protection and have a drain pan or bucket handy for spillage which can be collected and dumped down your home toilet or outside sewer clean out if you know its location.

Typically located behind the docking station in the outside, drivers side compartment. You will have to remove an access panel to get to it.

There is not a diagram available. The inside cover of the breaker box/fuse panel should be marked. If it is not you will have to power everything up and one at a time pull the fuse and document what is powered by that fuse.