Tritonman is about right, although I would say probably more towards the $300 price.
I was a Snowmobile dealer for over 30 years, and we just closed up operation last December. Dealers have no interest in machines of that vintage, so you have to find a buyer that is not only very mechanically inclined and able to do his own work, but also willing to scour the countryside for parts if needed.
The only new parts you may still be able to buy for it will be the standard run of the mill stuff like, drivebelts / sparkplugs / carb parts (possibly) / and other stuff the aftermarket boys still carry. Other parts that are more "machine specific" will only found at the "used" level, and many times, very difficult to locate.
With it sitting so long, my guess would be the track and many other rubber parts would need to be replaced, which ultimetely would cost more than the money it's worth.
There are the odd few out there that restore old sleds, but try to find the one guy that wants the particular one you have, and even then, he probably won't want to pay much for it. These guys do it as a hobby, so even the "collectors" don't want to put much into it up front.
In my opinion, your best way to get rid of it would be to find someone in your area that deals with the old stuff, and sell it to them for "parts", that's providing they are still interested in stuff that old. Not much demand left for those old girls.
REV