Hi,
There's a new customization and configuration manual available for Plant 3D and P&ID. The title is "Tailoring AutoCAD P&ID and Plant 3D". It is up to date for AutoCAD Plant 3D 2015 and P&ID 2015 but much of the customization does not depend on the version.
You can find the document here:
http://knowledge.autodesk.com/support/autocad-plant-3d/troubleshooting/caas/sfdcarticles/sfdcarticle...
One tip - the link on the page gives errors with some versions of MS Internet Explorer. If it does for you, save the file and rename it from .zip to .pdf. It's really a PDF
Peter Quinn
Senior Product Manager
Autodesk, Inc.