Clutch

How difficult or expensive is it to change the clutch in a 86.

First make sure the clutch is the culprit. The Fiero clutch system has many problems that can look like a clutch is bad.
Make sure its not your fluid level, leak in line, or slave cylinder.
Now if it is the clutch you have to drop the engine cradle and all, its the easyest way and quickest. Not as bad as it sounds, but get a good manual anyway to save some greaf. As far as cost goes I can't help you there, never had to replace one.