Redirect all your permalink structures! Check this out: http://yoast.com/change-wordpress-permalink-structure/. On the bottom is a generator that will show you what reg ex you need for the redirect. Then in the redirection plugin, just add the regex code to Source URL, click the regular expressions checkbox, and add the target ($4 or whatever the site says) to target. You’re done!
So my site broke for a little bit because I installed the Hikari Category Permalink plugin. I’m not to sure what happened but I ended up redoing my .htaccess, permalink structures, and reinstalling the plugin.
Needless to say it works perfect now, BUT in the process I figured out how to actually get my old category slugs to redirect to my new ones, 301 style! =D
So here’s how…