Use the 2.5 mm hex key to loosen the 3x8 mm screws to remove the motor plate.

Use the 2 mm hex key to loosen the 3 mm grub screw enough to remove the pinion gear from the motor.

Slide the pinion gear right off the motor's external rod when loose enough.

Make sure to have the pinion gear in the exact same area as it was on the replaced motor in order to align with the device's gearing.

This process can also be used to put an even better motor in as a replacement during reassembly.