Hey,
There really isn't much difference.... no difference in operation, just file locations.
In 3.0, the files used in the web panel are located in /usr/local/squidguard.... (if I remember correctly). In 3.1, the files were moved to /usr/local/squidGuard/www and has the updated e-smith templates to reflect the changes.
Just cleans up the filesystem a little. If you don't care about that, then it's no big deal. If you wanted to make the changes, just download the 3.1 tarball and extract. Then copy the template files over your existing template files, and move the web directory do the correct place. You should be able to take a look at the install.sh file and the directory structure of the tarball to figure out where everything goes.
Hope that helps.