On the right side of the tractor there is a small vent covered by a fine screen. It is covered by the piece of plastic that wraps around below the steering column. You can see the bottom of the screen just above the loader support.
That vent is in line with the clutch disk. Remove the plastic cover, then remove the two bolts that hold the screen on. Then take a long thin butcher knife, put the point between the clutch plate and the pressure plate, and give the handle a bump with your hand while someone (or a 2x4) is holding the clutch pedal down.
It worked for me. I had tried jarring it loose by running into a dirt pile, etc., but I couldn't believe how easily it came free with the knife blade.