If I remember correctly there are 5 torx screws that hold it on. Not sure what size they were but unless you can find a shorter torx driver you might have to pull the steering wheel off. Plus you will have to remove the airbag first. Follow the step in here to remove the airbag:
http://xoutpost.com/pdf/Heated%20wheel%20retrofit.pdf

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2011 X5 35i Space Gray/Black Nevada Leather w Dark Bamboo Trim
Convenience Pkg/Running Boards/Cold Weather Pkg/Comfort Access
3rd Row Seating/20% Tint/Style 215 wrapped with Toyo Proxes ST II/ LUX v4

2001 X5 4.4i TiAG/Grey Leather-Retired
djbock's Custom X Page!