Question for Sea nymph Boats

I bought a Sea Nymph Sport 470 in Dec 1998 from the factory incl. Dunbier trailer and Johnson 90 HP. Cost $31,590
Replaced new Dunbier trailer in 2010 and new road cover in 2016
I am wishing to sell soon and unable to ascertain a market price. Can you please advise a fair selling price for say, Trade me and is there any dealer to whom I can sell to or have sold on my behalf on commission basis
Really appreciate your help!