That sounds like a good deal on the gun, but you probably wanna look it over well before buying. You never know how someone cared for their gun. I have an old Mossberg and can attest that their good guns and tough as nails. I would hold off if I were you, and get it done with the 20 gauge. But then again, I'm thinking about saving up for a Benelli Supernova.
And I really didn't doubt that you'd enjoy turkey hunting. It's a blast!