D7000 AF perfect - FINALLY

As above in post 2, I decided to send my D7000 to Nikon UK based on the original post.

The estimate has come back and Nikon are going to replace the MIRROR DRIVING UNIT (1H998-128-1).

Does anybody what this actually does and should the repair improve AF?

Thanks in advance.

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http://www.flickr.com/photos/22051839@N02/