What did you customize? The 2.0 contains lots of filters that allow you change lots of things. So based on what you modified, maybe you can do the same thing through a filter now, and not lose any changes when there is an update.
If you uninstall you will lose the old db, so don't do that. You can overwrite the existing files in the wp store locator folder with the files of your modified version.
You do have to make a change in the db as well, look for the wpsl_version field in the options table, and set it back to 1.2.25 instead of 2.0.
Then load the settings page, this might show some errors at this point, some options where renamed, or removed with the 2.0 update, and save the settings again. If you save it again, and a field is missing a default value is used, and it should work fine.