the black cap is a ring shape 10-12 point star on the outside (diameter of a dollar coin) on the top (passenger side) and back of the engine block (next to the belts). I first had a hard time twisting it open by hand and eventually I did it with a plier/wrench. Be careful not to break it.
If you do it search on "PCV Retainer" and you will come across this post
http://www.automotiveforums.com/vbul...t=pcv+retainer
There is a picture of the diagram.
BTW, it is very easy and just be careful not to break the retainer ring. The PCV is totally hidden away... Help this help you.