I rebuilt the linkage on my e28 a couple of years ago, and the job itself isn't too bad, but in order to get at the bits that need work it was necessary to lower (not remove) the exhaust and the front end of the driveshaft. Some guys on mye28.com say they can rebuild the linkage with the exhaust & DS in place, but they either have little tiny hands or can do the job without seeing what they're doing. I haven't been very far under the X5 to examine things, but I'm thinking it'll be a similar story there.
On the e28, the bits that got replaced were
10
11
12 (includes 13 & 14)
15
There might be other wear items in there, like 2, 3, 4, 6 & 7, but given the fact that Autohaus AZ and Pelican Parts don't stock them (dealer-only?) I'm thinking they might not wear out as quickly as those directly involved with the selector rod.