We would also like to change this from "admin", as our auditors feel this is too explicative and would prefer a different name.  Is it possible?

I'll answer your question with another question: why are people logging in as admin? That should really be reserved for truly administrative functions, and not doing stuff with service forms that gets written to logs/history. It is very easy to create additional accounts that have identical privileges to the admin user (simply put a user in the Site Administration organization or give them Site Administration role). That way whatever names and login information you assign to these users would show up in

I think you would be ok with changing admin's lastname and firstname.

Our site is running 2008.3

Yes this is possible...we changed it at our site.   It requires a database SQL to be executed.   disclaimer: Our admin account has a personid = 1...not sure if this is by default...i believe it is.

To check, run: "select* from dirperson where personid = 1"

this should retrieve the admin account.

To update the first and last name:

update dirperson set firstname = '****' where personid = 1
update dirperson set lastname = '****' where pers