[Samba] SAMBA AS BDC

[IRV]

I'm trying to replace an existing NT4.0 domain controller with the
latest version of samba.  My concern is that I would have to re-create
all the users on the samba machine, change the domain name (From
NT-Domain to SAMBA-Domain) on each Windows 2000 workstation, and
re-configure every users email, settings etc....(We have about 500 users
with only 2 Admins.)
 
Is there a way to add a SAMBA BDC to an existing NT Domain, have all
user names / passwords transferred to the SAMBA BDC, and then promote
the Samba BDC to a PDC, throw away the NT PDC, and standardize on SAMBA
Domain Controllers?