Welcome.....your description is almost nearly identical to the condition of my '86 when I bought it 3 years ago for 4K. (except for the back hatch covers ) Being its through a dealer there is definitely a mark up on it as opposed to buying directly from a seller. Also keep in mind it is a 1991, albeit still a 20 year old boat it somewhat newer than alot of the 70's and 80's boats. My opinion is if he is at $5500 I would be shocked if he let it go for $2500 or 3K....Definitely cant hurt to try....what part of the country are you in? that also has a little bit to do with it. NY/NJ. VA and FL are crawling with V-20's as opposed to midwest, or West Coast.
Ferm's probably right about the chance you are taking buy not running it. I actually took that chance when I bought mine....the compression was good, outdrive had not water in it just didnt want to idle well. Ignorance and trust in the seller (and tired of looking at boats) made me pull the trigger and thank god it worked out....pretty sure I would never do it that way again. Good luck with whatever you do.