I think you will have to uninstall the current version even if you go to google play, but by all means try that.
If you do reinstall you will need to run the wookie again although you could try backing up your current configuration to an sd card and restoring after reinstalling kodi.
Future updates should automatically update from google play over the top of the new installation i.e. you will not need to set up your addons again.
As to the source of your error, a suggestion from the official kodi forum is that your 15.2 is somehow "unofficial" (perhaps it has been customised in some way) hence the conflict. Did you buy the t8S from droidbox? This might be important information for other users trying to update.