yes... I seem to recall that that is the way it's done...
unfortunatly I don't have access to an excahnge server anymore since the place I work now uses IMAP mail due to greater flexibility.
but IIRC...
go to the users and computers pannel, and view the properties of the person you wish to change,
their display name should be on the same page as the rest of their details, including default mail address login name etc...