Gentlemen, the rearview mirror on my 2000 XK8 convert. is black half way up. Is there any cure, and if not what's involved in replacing it?

 

Wrong forum. You want the X100 forum.

You have a Gentex mirror. They had problems with them in the early 2000's and did offer some sort of warranty/exchange program. My guess is their extended warranty expired long ago though. Next best is advice is ebay. There are quite a few mirrors on ebay now.