Several ideas.. Step one, Obtain a good (not need to be expensive) Multi-meter, 10 to 20 bucks at Harbor Freight will do the job just fine.
Now find the HOUSE batteri4es, You have two "Sets" of batteries One for starting the engine, one for the "house" fund the house set, this is often more than one battery wired either in series (six volt batteries) or parallel (12 volt) measure the voltage (KEY OFF) from the negative terminal with wires running somewhere other than to another battery, to the positive terminal that has wires running somewhere other than another battery. NOTE and report voltage, if any.
Now look for a switch, OFTEN it is just inside the door but it may be on dash or a control panel elsewhere in the coach. It may say "USE/STORE" or it may say "AUX" or it may say "MAIN" it may be a toggle or a 3-position center off rocker with spring return to off.
It may even be a rotary switch (Fairly big) or a kinfe switch on or near batteries.
Tell us about this switch, and play with it. (Only if you have voltage on the batteries)
We will go from there.
As to blowing the breaker on the house.
Step one Is it blowing breaker or tripping GFCI? (or is breaker a GFCI type?
If YES, post
If no, then Step 2: Turn off ALL circuit br4eakers inside coach, plug in, if it does not trip turn on coach breakers 1 at a time and note the results. (also which breaker it was) post results.
When house breaker trips, turn OFF that breaker, and reset, then continue with the next breaker.. If it trips on a later breaker again turn off, reset and note the breakers that trip the house. Post
We can take it from there if this does not tell you what is happening.
Home is where I park it!