The Bentley, while very good in many areas, has very little to none about the AOS.
The best guides for that are the 101 Projects guide:
Pelican Technical Article: Boxster Air / Oil Separator Replacement - 986 / 987
Pedro's garage guide:
Replace the Air/Oil Separator
And there are several good threads in the DIY section on this forum that have updated steps, shortcuts, etc..
Steve
Edit: here is one of the threads from the DIY forum:
AOS replacement tips