[Samba] Samba PDC (and Users/Machines) join Server 2003 Domain

[Mike]

I've been reading the Official How-To, Chap. 6, Joining an NT4-type Domain
with Samba-3 because I want to join my current Samba3 PDC server and all its
users (on Win XP Pro machines) to an MS Server 2003 domain.

Not sure if I am understanding the material.
It seems as if I can join the Samba3 server to the to the Server 2003
domain, but not all the user accounts. Is this correct?

What I want to accomplish is --- Maintain the same Samba PDC and user
account setup, and also make it possible for the Samba users to access data
in a directory on Server 2003.

I appreciate any points of advice and suggested reading.
Thank you for your help.