Your current propane setup for your firepit almost certainly has a regulator on the 5 gallon tank and then a low pressure hose from the regulator to the firepit. All you have to do is disconnect the hose from the regulator, hook it up to a quick connect adapter and a valve and connect it to your coach's external propane fitting.
Amazon has all of these fittings for $20, much cheaper than Extend a Stay-
https://www.amazon.com/Propane-Conne...s%2C194&sr=8-3
David