emead-
This is somewhat of a guessing game!
Some thoughts:
We have an archived set of previous boat ads for C-Dorys available
HERE that can be used for comparative purposes.
The 1982 boat is a "Classic" model that has a short cabin, large cockpit, flat bottom, and more utilitarian design than the models produced from 1987 and beyond. They are usually priced a little lower that the later models.
The value of the boat largely depends on it's condition at that age. The C-Dory boats last forever in terms of hull sturdiness, but the cosmetic appearance of the boat, the condition of the motor (and whether it is a two or four stroke (the later being more desirable), the age and condition of the electronics, the additional equipment on the boat, and the trailer type and condition ... all make a large difference in the price.
Some will say that older, dated electronics and a 2 stroke engine are not worth anything, as they would intend to immediately replace them with a modern fuel-injected four stroke motor and all new electronics.
But if the motor and electronics are usable and reliable, and within your plans for the immediate future, you don't have to think that way!
Just as a crude guess, the boat could be fairly priced anywhere from about $12k to $18k, more or less, largely depending on condition.
After you look over the comparative archived ads, you'll have more of an idea of what the used boats of that vintage go for.
NOW FOR ONE OF THE BEST PIECES OF ADVICE I CAN GIVE ANYONE BUYIUNG A USED BOAT. THIS WORKED SO WELL IN OUR SAILING FLEET WE MADE IT A FORMALIZED PRACTICE.
Get someone who is already a seasoned boat owner of the same model/make/type, etc. boat to go with you to look at the boat you're thinking of buying. Someone who has owned one for 5-20+ years knows all the ins and outs of the boat, equipment, trailer, and repair / replacement aspects of ownership and can give you invaluable advice and counsel on your purchase- even to the extent of saving you money on state sales tax, etc.
I don't know where you live, but there must be a knowledgable C-Dory owner somewhere around! If you're anywhere near me, I'll be glad to help out!
Good Luck, and don't be afraid to ask more questions!
Joe.