1) Do I need to turn off the KDE stock desktop effects to run the Compiz 3D desktop?
Yup - I believe it's better to switch to only having one set.
2) what keys do I use to view the cube, cylinder, etc.?
Plenty on the web about which keys do which - and tutorials as well. (and I
think the advanced options in Compiz mention the keys as well)
Did you install all the compiz plugins as well? They add more functionality/uses/themes etc to Compiz
Also, have you installed the Fusion Icon as well? (
fusion-icon - Description = Simple tray icon for compiz fusion)
Fusion Icon lets you set the Window Manager (and Window Decorator)
If you install the Fusion Icon I think you
may need to restart your desktop - when you run it from the main menu the Fusion icon will be placed in the panel from where you can set various options.
Also, you may want to go to
Configure Your Desktop > Workspace Appearance and Behavior > Default Applications
and set the Window Manager to Compiz