Hmm, someone e-mail me about this today as well. And I'll say the same thing here:

First suggestion, dump PHPNuke and go with PostNuke. PostNuke overall is
better, and unfortunatly I discovered it after setting up PHPNuke. There are
numerous reasons I say this, including several hundred lines of code in
RioCar.org to fix some "issues".

Both PHPNuke and PostNuke are free, and work on all free software. They both require a database, and may require a specific one like MySQL.

Play with PostNuke on a test machine that you have control of before trying to move it to a host. It takes a bit of work to get perfect, and PHP knowledge is definitly needed for any heavy changes.