The photo below is of a 2824 but the 2783's method of stem removal is the same to all intents and purposes. Pull the crown out to the second position to "hack" the movement, then between the crown and the upper crown wheel (the one with the large blued screw on top) you can see a hole containing a button with a slot across it. Get a 1.2mm screwdriver (red top) and press it into the slot whilst pulling on the crown, the set lever will disengage from the stem and the assembly will withdraw. Refitting is the same as removal just be careful not to use too much force pushing the crown home before you press the screwdriver in the slot. Try gently rotating the crown back and forth as you slide it back in to line up the square section of the stem with the clutches slot, you can dislodge the yoke if the stem isn't far enough in which will mean quite a bit of disassembly to resolve.