[Samba] PDC and "group" question

[MargoAndTodd]

Hi All,

   I just upgraded a workstation server to a PDC server.
I am using tbdsam as my user database.

Question 1:  As a workgroup server, I created my groups
in /etc/group (groupadd).  Is this still the case?
Do I also need to tell Samba about a different database
for groups?

Question 2: occasionally I get asked for the user
with "administrator's" privileges.  Do I need to create
a group called "administrators" (with an "s") and
populate it with "root", "todd" (me), etc.?

Many thanks,
-T