I've just finished installing GT-NextGen on this site.  The goal of this modification to PHP-Nuke is to "htmlify" the links on the site so that sites such as Google will index it properly.

It was a pain to install because it required modifying a lot of core code (not huge modifications, just on several files).  The biggest problem I have with those types of modifications is that when I update versions, I have to redo it all.  This is the reason I'm trying to make the fn-comments modification I'm doing hold most of it's code in a seperate file.

My next goal is to find where to modify the Meta keywords in PHP-Nuke.  It's not that it's going to be hard.  I just haven't done it yet.