AS a WV resident, I can say there are few places in WV that specialize in diesel pushers. However, it is a state full of heavy equipment to support the mining industry.
The most prominent place I would go if I had an engine related issue is Western Branch Diesel. Authorized DD. I have been in several of their shops and I was impressed. I saw a few conversions in and around the parking lot. I talked to a couple of mechanics and they didn't talk like buses were uncommon at all to them.
If you are in my area, I'm well stocked with tools, and GoJo.
Richard Rhonda Ty and Alex Entrekin
1995 Newell # 390 DD Series 60, Allison World Trans
Subaru Outback toad
Often wrong, but seldom in doubt
Rhonda's chronicle https://wersquared.wordpress.com/