IMHO: Certainly possible but not likely that your 300D would fetch 4 grand. As a comparison take a look at Tyler's very nice 300D for sale on this forum.
1985 300D: Ol' Turbo 198k, Wichita, Ks $3995.00
Unless yours is in comparable condition, or better considering yours has a bunch more miles on it, you would be extremely fortunate to find a buyer at that price.