Is this existing layout another CMS system? Without knowing the details I can't really say yes or no, it all depends on what you're integrating it with.
By multiple users do you mean one person having multiple user accounts?
There's some good online documentation here for installation
http://ez.no/developer/ez_publish_3/documentation/ez_publish_3 eZ publish also comes with a web based setup which should make it fairly easy to install.