Since you're comfortable with the engine stuff, you're way ahead.
House items:
1. Propane system - since you don't have familiarity, take it in to a shop and have them test it. They'll check all the lines for leaks as well as the appliances that use it.
2. Get your house battery up and running. I bought an optima group 31 blue top AGM battery and have been very happy with it. It has not given me any trouble and is enough battery to get me through a week of 1975 camping type use (plus recharging cell, kindle, laptop).
2. With the battery in place, you can now see if your converter/charger works. First thing here is to look at the power cord that comes out of your RV.
Is the plug on the end similar looking to a clothes dryer plug? If so, then you have a 30amp setup. If it looks like a regular outdoor extension cord plug, then it is a 15amp setup (not common, but I know people who changed out the plug to a 15amp so it can happen).
OK. If you have the 30amp, you need to get yourself a 30-15amp dogbone. Should have the 15amp plug on one side and the 30amp female outlet on the other. Don't get the "puck style" as they don't handle as well. NOW you can plug your RV into your home's 15amp system. ABSOLUTELY DO NOT plug your RV into you clothes dryer's 220 outlet!!!!!!
Once you have it plugged into the house system, you can test. If your overhead lights work when you are plugged into shore power and when you are not, your converter is working properly.
If your overhead lights work on shore power but not when unplugged, then you have a charger or converter problem.
If your overhead lights work when unplugged but not when plugged into shore power then you have a problem with the converter.
Basic definitions:
Charger - charges the battery when plugged into shore power. Usually the vehicle's alternator is run through this to charge the house battery while driving (but some bypass the charger).
Converter - this takes the 120v power of the shore power and converts it to 12v power to run the 12v system in the RV. Your overhead lights and water pump are the 12v system.
Inverter - you 98% percent don't have this. It is common now, it wasn't then, so unless it was added aftermarket by a prior owner it's not there. This inverts the 12v power into 120v power to run the outlets in the RV. Note: the outlets work only when plugged in to shore power, a generator, or if you have an inverter.
Your fridge, if original, will run on propane or 120v power. Your stove/oven will run on propane. Your furnace will run on propane, however the fan runs on 12v - and the fan will run your battery down very quickly.
Your water pump will run on 12v power.
Your charger is likely an old style single stage. Nowadays, the smart chargers are much better. So, if your converter or charger is bad, just replace it with a new progressive dynamics charger/converter. The cost is worth it.
OK that will get you through the basics of the electrical.
Oh, and your chassis per the VIN is a Dodge MB300. You'll want that when looking for parts.
