On the docs site, you can follow the steps there to upgrade from past Cacti version to current one:
http://docs.cacti.net/node/7
With that, you should also be able to fully rollback if upgrade is not functioning for you. You can apply this to the CactiEZ CD, downloading the 0.8.7a version from the html folder:
wget
http://www.cacti.net/downloads/cacti-0.8.7a.tar.gz
and follow the instructions.
There's also documents making use of Ubuntu Linux to install Cacti. Either way, you can create the update, and rebundle it for your own archive also. That way you can restore the past image if all else fails, and also use it to create other Cacti sites (until the clustering portion is out where multiple cactii can work together from a central DB, which I'm waiting on, along with version 0.9 (date for that is a big ole ??? currently from what I see)).
To create your own CD, you'd follow the notes on the site:
http://cactiusers.org/wiki/CactiEZRemaster