Considering the machines age, if you are not mechanically inclined, I would take it to a dealer to have the machine and trailer checked out. Ask to see the receipt for the SC rebuild to prove it was done. Very expensive if this fails and ruins your engine.
Price depends a lot on where you are and condition of machine. For the eastern Mass area if the hull was not painted, hull and seats are in good condition, with a trailer and cover, private sale price would be 4-5K. If you are dealing with a dealer who will provide a warranty, it would be worth more.
Check the trailer axle for signs of rust in the area of the spring mounts. My 2005 cracked last year requiring a tow to get it home.