It might just be the stiction you would expect from a lack of use and lack of lubrication.
You could first try some Judy Butter or a Silicone spray.
I wouldn't put more money into the fork. Prices have come down as performance has increased so a new fork is a good idea anyway. Try to find a fairly short travel fork to suit your frame.
Note that if your bike uses a 1" headset, a replacement fork will be a little more difficult to track down, 1-1/8" being the current standard. I do think GT went to the larger size early on in the game but I could be wrong.