You should be able to install the updated game over the old version without problems, but it might be an idea to be safe, just so that if something goes wrong during the install (unlikely but possible), you will still have your backups.

Here's the FAQ for backing up the files - it's for Windows, so if you use a Mac you'll have to change the platform on the FAQ page. Remember also that the install will ovewrite any mods you might be using, so it'd be a good idea to backup the \images folder as well, so that you can reinstall the mods easily.


See also Arthur's announcement.