someone school me on the vanos system and parts needed for fixing it

[flekz]

I have all the symptoms of a bad vanos.. marbles in the can sound on start up. low end torque loss. I just want to know what parts are needed for this. I know when I replaced my chains on my vr6 years ago I had to change the chain tensioner and chain guide rails. so I have to do this also for the x5? also is the vanos just a sensor? or what because I'm not exactly sure how to go about this because I haven't really researched much for this issue. I have many years mechanical experience so to do the work its nothing for me, but I definitely want to know what parts are needed for this...thanks guys any help would be appreciated