...I'm going to go for the obvious answer to every 80s space game request here and say :
Star Control 2?
It's not 100% accurate to your description. The ships isn't quite tuning fork shaped, but you can land on planets and sell stuff to other ships (Melnorme). However, the lander graphics weren't 3D and this
was the sequel.
Star Control 1 was nothing like it for the adventure aspect, but I dug the stragety game even more (if that's possible).
Then there's always
Fibs and Brags, a self proclaimed Star Control fan game. The web site is a bit broken right now so I don't know how to download it, but I'll see if they can't get that working soon. But maybe the
screenshots will be enough to tell you if this is the right game.