Boost motor tear down and question on replacement parts (gear removal/replacement)

I have some boost external motor from a friend. Connected to the hub, they're completely dead. https://preview.redd.it/1ly78yog553h1.jpg?width=629&format=pjpg&auto=webp&s=90d6e814f72588a52f04adda01346ef86cea94f8 Opening and checking results in a suspect, a short circuit in the motor or at least some current overdrawn as the PTC is triggered (it is a 0.2mA resettable fuse): https://preview.redd.it/8dsdfsog553h1.jpg?width=240&format=pjpg&auto=webp&s=ba6b92d2ec1cbe0ca7af0c43bea70311fa6dc106 If...