Hello ChicagoMusicGuide,
Using FTP you can update the theme and no any changes will be back. We think all the code changes are made on the child theme. So, if you are interested on theme update, you can use FTP so that no any setting will be back. You can first on demo server too. But make sure, no any code edited on parent theme. If you have edited parent theme, all the updates method will change the code.
Thanks