Have an opportunity to pick up a 1983 Martin D18 from a friend's friend. It's a 1983 (150th anniversary?) D18 model, description being "super clean, ready to be played - no nicks/dings/bruises and the neck is great. Will just need a new set of strings." It includes the factory hardshell case. What do guitars of similar description typically go for? It's a Martin, so even the worst model possible is still going to be a pretty darn good guitar, but where does the D18 - specifically the '83 model - land on that scale? Wondering if it's worth the investment.