Well my buddy got a 1978 ski doo everest from his grandpa. The sled has not been driven in 15 years just stored in the shed with out any gas in the tank, and the engine was fogged. we got the sled running with a little tlc and it is in mint condition. no rips in seat only 1500 miles and no cracks in hood or windshield. What should this sled be worth?