Using the latest avail P96 from the 3.9 CD. I know an Alpha version is available that's unofficial but am a bit scared to install it. Will it update my current install and leave my working screen modes alone?
That is a very good question. I actually didn't know there was a version of P96 on the 3.9 CD, when I installed mine I went straight to the new version on the web. Keep in mind that anything on the CD is probably going to be as old as 2001-2002, whereas the one on the web says it was last updated 1-NOV-2014.
Usual disclaimer about updates applies: it probably fixes a bunch of bugs, and adds a bunch more in the process.

If you're concerned about mucking up your current settings, you could probably make a backup of your ENVARC:SYS/screenmode.prefs and the contents of DEVS:Monitors, just to be on the safe side.