I have not taken the time to check on your parts list . the actual oil separator on the X5 is the bottle which is connected by a hose to the camshaft cover . the oil drains through a hose on the bottom of the bottle . the gasses go through another hose into the cover you mentioned at the rear of the manifold , same thing shown on the video in the link for the 7 series . this cover holds a diaphragm . the diaphragm will fail at some point in time due to the soft rubber from which it is made .
there is a shortcut repair possible on the 7 series whereby you can remove the round section which houses the diaphragm instead of removing the entire cover . the round cover requires replacement because it gets damaged during this removal process .. so you still need to buy the complete part but carefully remove the round cover and diaphragm from the new part . best to just fit the complete part on an X5 as access is easier .


EDIT ...... found a link showing the shortcut .
http://www.bimmerboard.com/forums/posts/816587