Hi,
I'm sorry but you will need to have a Certified Xerox Technician onsite to log in as a technician and then he will be able to reset the Administrator password.
I know you said you've looked online for the admin passwords but for the sake of clarity, here is the two standard used for Xerox Office machines:
For your 7328 specifically, it should be:
user: 11111
pass: x-admin
and the most used now is:
user: admin
pass: 1111
Hope you success!
K.