Sorry. I realized I didnt answer your question. You are actually just replacing the gear INSIDE the actuator. BMW would want you to replace the whole actuator for big money. But 99.9% of the time its just the gear inside that's stripped. When you take the gear off, you'll see that it loos like the gear teeth have been melted away in the middle. Its way easier than it looks to replace.
Trust me. You'll be saving thousands of dollars on this simple fix.