To uninstall MyMuse, go to Extensions->Extension Manager-> Manage
Filter on the word MyMuse. Choose MyMuse Simple and Uninstall. it will remove all plugins and modules as well as database tables.
You need ONLY SELECT MyMuse, the Administrator - Component. It will remove the component, all database tables, all MyMuse modules and plugins.
After uninstalling it will present a screen with information on what was done.