Before dismissing the coach completely check the headliner to determine the reason for the failure. If you see water stains then you have a water leak. If the foam in the headliner has become a crumbly powder them the headliner material has failed, not an uncommon event.
This is assuming that the headliner itself is similar to an automobile headliner. Most auto headliners consist of the exposed vinyl or woven fabric glued to a foam backing. The foam degrades over time which lets the liner material sag/hang down. In a car the headliner itself is glued to a molded cardboard piece that gives it it's shape. To replace the headliner you have to remove the molded cardboard piece and scrape of the old headliner and glue on new material. Headliner material usually comes off of a roll about 54" wide and is available at automotive upholstery supply shops and many sewing supply stores.