Going and doing the test drive was an awesome experience that more should do.
I expect it was running to help seal up leaking exhaust manifold problems.
Keep looking at different options. From my personal experience with an old MH it does seem one will need to spend around $20K to get a MH not worn out and that is based on current technology chassis wise but there can be exceptions.
While it took us a few years to get ours to the point we had it for our 8000 mile cross country it ran fine and other than the front air bag failure (they were 10 years old and should have been replaced before the trip).
There is always the down side of loosing an engine that replacing would cost near the value of the MH BUT if we get a nick or even worse it does not cause me a lot of stress as long as it does not effect dependability.
The quality of our trip and how the kids will remember our MH trip of a lifetime will be no less because we only paid $7995 for the unit. The fact they have been involved with most of the repairs and upkeep the prior five years made the trip even more special and they have gained life long repair skills.
Do not give up on you plans to do a cross country trip.
We're definitely not giving up on the trip, but I think we're leaning way towards getting a towable pop-up. I don't think I can put $20k on the line in the event of a wreck or breakdown that would require even more cash.