The first thing to do is disconnect the clutch cable from the arm on top of the bellhousing. Mark where it was adjusted to so that you can put it back in the same place.
With that disconnected, does the pedal move smoothly. If so, then its a gearbox out job to remove the shaft or change the clutch. Even if its the shaft, the clutch should be changed while your in there.
If not, then remove the cable from the car end and check that the cross shaft is moving smoothly. If so, replace the clutch canle, and check the engine earth strap. The clutch cable can become an earth strap if the original one fails, leading to seizure.
Cheers
D