Do a web search for "toyota motorhome" some sites should come up. Other than this site I haven't seen a site specific to Toyota based RVs. Any vehicle is worth what the buyer will give. A decent 90 Seabreeze should be worth $4,000-$10,000 according to what they are going for on E Bay. I recently bought a 1990 Dolphin for $1400. It is mechanically excellent with a similar drive train to your rv but in need of major structural (wall/seam) repair. I am glad the work is about done as it is not for the the faint of heart!
Good luck with the sale.