Remember that dealers (car, tractors, or whatever) will always offer you less because they want to make a $ on the resale. You are always better off to try and sell privately first.
Try an ad in your local paper or shopper type paper. Set a price more than the dealer is offering you, but a little less than the dealer would resell it for. Careful of checks, even "certified checks." Too much fraud out there.
regards,
Steve