There's currently no built in option to alter the presets. You can, however, copy them over to "Custom" and change the code to your liking. If you're telling me which preset you want to alter, I can look up the relevant code for you want.
The update is not required but strongly recommended. But as @Freelancer said, it is really easy. If you don't use any custom loading icon but a preset, it's just installing this as a new addon rather than upgrading an old one. If you do use a custom loading icon, all you need to do before that is to copy you settings to somewhere and copy them back in after the upgrade.