If you have some canned air, you have "Tool 104" as this was simply an air pump that popped the crystal out via air pressure. You first remove the crown and the crown side of the split stem (pull the crown to the setting position, then pull further on the crown and it will snap apart), the put canned air or a bulb style blower over the case tube, and apply pressure - the crystal will pop out. Then use a small screwdriver to push the stem back to the winding position, and the movement may drop out at that time. It also may have a ring inside that needs to be turned to release the movement clamps, or the movement itself may have to be rotated in the case. There are a couple of different styles for this system, so once the crystal is off you can see what is needed.
If you have no experience doing this sort of work, I would highly recommend you take it to a watchmaker to have this done. In any case replacing the crystal will require a press to do it properly.
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