I just installed zope and plone on a new Kubuntu installation using the Adept package manager. Zope comes up on port 8081 -- which was a bit of a surprise, as I expected it to be on port 9673 as in other Debian distributions -- but I can deal with that. 8080 is standard port for Zope. You may change it in zope.conf file.

The problem is I don't know the admin username and password. Is there a way to either find out what they are or to reset them to something known?

you may run ./zopectl from your's <zope instance home>/bin and execute adduser command in the prompt (be sure that zope is not running) to add new user. Other thing is that I think it is better to install zope from sources. Then you have control on what is installed, where and what is user account. -- Maciej Wisniowski