If you're talking about the Moodle plugins db - then yes you will need to register a new plugin. you can update the description of the old one to point to the new one. You may also want to write some form of upgrade/conversion script to allow people to upgrade from the old plugin to your new one.
Here's how I managed the change from mod_attforblock to mod_attendance - it might be useful?
It's a bit nasty and is really an abuse of verison.php but worked ok - I then eventually removed it from version.php