I've had my 2007 391 for over three years now and just got back from a 1,000 mile trip. I've replaced the water pump, lost the cover on the generator, replaced the airconditioner exterior cooling fan and had the shower J-trap crack. That's it. I'm not bothering to mention the few bulbs that have burned out, or the idiot stuff I've done making me replace the TV antenna.
The water pump irritated me cause I'm low miles but a frequent user so no excuse for a failure. The A/C fan could have been debris but it was a cheap and easy fix I did myself. The J-trap was a factory worker totally neglecting his job.
All my fixes took a day at the shop or a few hours by me. My mechanic has actually talked me out of some preventative maintenance I thought I should do. Workhorse really didn't give us the greatest p.m. schedule.
The first thing I would do is get a new shop immediately. Months in the shop doesn't sound very competent to me.
2007 391TS UFO Chassis