I was able to order the worm gear part and replace it with a new one. I was not able to remove the external gear to replace it. I ordered five parts in all but really only needed one. I would have rated it as an easy job if it didn't involve having to remove the messy planetary grease; however, I knew it was necessary to get out every little speck. Replacing the fresh grease was just as messy. Finding a specialty tool, the ring pliers, to remove the c-ring from the shaft was difficult. The part had smaller holes than the pliers' knobs. You cannot complete the job without those special pliers.