There's an article in the X5World home page describing the parts and installation for a 4.6is/4.8is conversion.

http://www.xoutpost.com/articles/x5/b...3-0i-4-4i.html

If you're thinking about it now, you'll be kicking yourself later if you don't upgrade to the 4.8is bumper. Go for the rear bumper conversion when you get the chance. The 132's are fine - there's plenty of folks here who think the 132's are the best looking OEM X5 wheels.