Yesterday I helped a guy from the BF.C forum replace both his air springs on his E39 Touring in under an hour. So I though I would post the link to the write up that I did last winter for you guys to use as well. BTW the procedure can be used on the X5 or any of the cars with air springs.
http://forums.bimmerforums.com/forum...d.php?t=942496
Cheers!