well, as was mentioned before, I'd look into the Bentley manual.
Personally, I know a fair amount about cars (I've worked on lots of VW's, Hondas, Toyotas, Dodges and Fords), but just got my first BMW 2 weeks ago, so I don't know too much about BMW specific maintenance (e.g. exactly where the ICV is). My Bentley should be coming in the mail on Friday, so I should be able to give you that info later on.
As for finding the vacuum leak, that can sometimes be like finding a needle in a haystack. The best bet is to diagnose the symptoms of the problem, find the part associated with the problem, find the vacuum line(s) associated with that part, and inspect them. Sometimes you'll be able to visually find the leak on those hoses. The real bad leaks will be visible.
I know that it's vague, and I'm sorry about that, but I guess that once you find your ICV you'll be in good shape. Sorry that I don't have a bunch of good info for you.