As a member of the ancient motorhome owners group...
Yes, I bet the fuel in the tank(s) has gone bad. If you can't get the tanks emptied and refilled, it might be possible to rig a temporary fuel supply to get the rig home.
While that alone may be your current problem, be ready, if they have not been replaced in any recent decade, any rubber part is likely to be a problem. The most apparent of these will be the fuel lines that were never intended to put up with the stuff they sell as motorfuel these days. But, the most important to watch will be the rubber brake lines. These can fail lots of way and some don't show. The brake fluid should be flushed even if you don't change out the rubber lines.
Matt
