Steve,
Enjoy the journey. Both in your quest for the perfect coach and memory making once you own that perfect coach.
Cost of ownership, focused just on the maintaining coach and it's systems can be all over the map. It really comes down to past maintenance, care, and how close periodic replacement items are coming due for replacement. Some items can be expensive, like tires. These are million mile chassis, so expect a well maintained 25 year old coach to still give years of use. Given you are looking at a 92, you will be looking at a 8V92 powered coach. I'm not that knowledgeable on the 2 cycle Detroits. I think most would tell you that you don't have to steer clear of that engine, but if your budget can get you into a 94/95 with a Series 60 you are making a better choice. 8V92 mechanics are getting harder to find.
What is on your want and needs list? That can help. As for Angola, they made some nice conversions. They, like many others, are out of business, However, that shouldn't be a deterrent given these were simple conversions with little if any need for specific Angola information.
Many charter bus operators are experienced with Prevost coaches and many do accept outside work. So, being in WV should not be that big of a deal.