I'm not a very technical designer when it comes to dotnetnuke, focusing more of my attention on skins, graphics and flash. However I decided today to make an attempt at upgrading the core framework for the site from version 04.05 to 04.07.
It's done, and seemed to go successfully. Below are a couple of links to blog posts highlighting how the upgrade process should be done.
Upgrading DotNetNuke by Eric Van Ballegoij
App_offline.htm by Scott Guthrie