'svcs webmin' showing webmin as disabled does mean that you have webmin installed. About the 'maintainence' status:
Quote:
MAINTENANCE The instance is enabled, but not able to run. Administrative action is required to restore the instance to offline and subse-quent states. The maintenance state might be a temporarily reached state if an administrative operation is underway.
This is from the smf(5) man page. You can run svcs -x to see the status of services that are not running (in this case webmin). After you find out why it is failing, you can do whatever is required in order to start the service.