If you no longer plan to have or use a hot tub, I would just replace the breaker that supplies one of the legs of the 50 amp service with a 30 amp breaker and also replace the receptacle with a 30 amp RV receptacle that you can get most anywhere, and then you can just plug your coach into that receptacle without having to concern yourself over an electrical problem. That 50 amp receptacle is two legs of 25 amps each and they total 50 amps so that a coach, (or a hot tub), can use both of those legs to get whatever power they need to supply the high current needed in a 50 amp coach. That 50 amps is a conventional voltage and current source that can be used by coaches and households. A 30 amp coach receptacle is more commonly used in coaches that are equipped for it, as yours is, and if you use just one leg of the 50 amp service that is currently provided to the "hot tub", and replace the breaker with a 120v/30amp breaker, and then wire the receptacle using that line, while tying off the other line, (pull the breaker for the other leg), you will have one 120v/30amp leg, one neutral line, and one ground line, and you are go to go without risking any electrical error that would damage your coaches electrical system. If you want to leave the 50 amp service in place, you could also do that by pulling a new line from the breaker box to the receptacle box and adding a 30 amp receptacle in that box and a 30 amp breaker in the supply box and that would then give both the 50 amp and 30 amp connections in the same receptacle box, which may also need to be changed in that case. Best of luck, and if you are not familiar with electrical codes and methods of installing that kind of thing, I would heartily recommend asking an electrician to help you out with that chore.