Hello,
It is not possible to install the newer version of JoomSEF over the older version using Joomla! installer. You will need to either replace the files manually and check the tables structure, or remove the older version first and install the new one.
Your currently created SEF URLs won't be lost when you uninstall JoomSEF, but the tables will be renamed (_bak suffix will be added), so you will be able to manually move the data to the new tables created during installation of new version. You can also export your SEF URLs and import them again in the new version.
Best regards,
ARTIO Support Team
