The drivers rear door carrier part# 51228243635 is what you are needing. Fits 00-06 X5. I just went through this myself and it took me a while as I ran into a few snags on removing the side privacy trim, removing the old carrier and putting the handle end cap back on and getting that Allen bolt to line up with that cap. I went with an aftermarket carrier kit which is probably why I had a few issues aligning up with Allen bolt. But than again from what I hear its hit and miss as Ive heard some state they had no issues with aftermarket what so ever. If I had to do it again I would go with a OEM carrier! That's just me. I think now that I know what to expect and how the pieces go in and out I should be able to do this pretty quick.

Let me know if you want to tackle this and Ill assist as best as I could.