I can't help you with MaxWebPortal, but I have installed PostNuke a couple times. The install script does nearly all the work for you (at least it did for version .723.
The bad thing about PostNuke is that there is so little documentation out there. After a lot of digging, I found "PostNuke for the Absolute Beginner" at http://postnuke.bloodymongrel.com/. It's a step-by-step guide to installing PN on your system.
My first install was a pain in the butt, but it's really not that difficult. One of the biggest pieces of advice I can give is to set up your MySQL subdomain, user, and password at least a day before you run the install script... otherwise you might experience PHP errors since the database might not be there.
Is this for your two posted sites? Let me know when you've got them operation, I'm always interested in how people can get PN personalized. Good luck!