$500 is about the average cost of the M3 SMG II wheel with paddles, excluding the airbag. Like Bimmer360 says, its a pretty easy mod, just take your time and print out these articles:
http://www.xoutpost.com/articles/x5/i...003-style.html
http://www.xoutpost.com/articles/x5/i...-wheel-x5.html
http://forum.e46fanatics.com/showthr...threadid=63211