This mod was done on my E39, 540i, but it's the same procedure on the X5. It took me about an hour to do this mod. SMG steering wheel with the mulit-colored stitching. The steering wheel, trim, steering column, and center console all need to come off for this conversion.
Got the steering wheel from Crevier, airbag from ebay, and the retrofit kit from mr.paddleshift.com. Total cost was about $1200. I hope to recover some of that cost from selling the old wheel & airbag.
Here's some before & after pics. I'll be glad to help if anyone is considering this mod.