Price depends on the state of the bike and what components/fork are on it. For a two year old stinky in good condition I would say around 7 or 8 hundred is probably fair. Maybe a bit more if the fork/components are higher end.
I think stinkys are meant to be all-mountain/freeride bikes. They have a decent amount of travel and should do fine for downhill applications but may be a bit heavy if you are planning on doing a lot of climbing.