Well,
Aside from all the hoopla about how dealers/repair centers "should" perform, I thought I'd throw this in the loop. The repair center in question, stated that the likely cause of the vibration the OP felt in his coach is a "carrier bearing" on the drive shaft. That bearing is also commonly referred to as a "Center Support bearing" too.
And, it's normally a very common bearing. I've had more than a couple of them go out. Each time, I found one in less than about 10-15 minutes of phone calls to auto parts supply houses. Now, I don't know Holiday Ramblers very well so, based on the fact that it has a center support bearing or, "Carrier bearing" as it's referred to here, I'm presupposing that it's an A with a front gas engine.( I suppose it could be a FRED too). Did or, does, Holiday Rambler make a class C too? They also have center support bearings.
Now, either the center support bearing that the chassis builder installed is some kind of odd bearing and not the most commonly used ones, or, the RV repair center is lacking a bit in obtaining that bearing. There's a few zillion bearing supplies outlets across America and, I'd surely think they SHOULD be able to find that bearing in waaaaaaaay less than TWO WEEKS!
It's a bearing for Christs sake, not a NASA Space shuttle part.
Scott