[Samba] SAMBA BEHIND A FIREWALL

[tatkins at ieselc.com]

I have setup a server with samba on it behind a firewall, I am trying to
create a PDC to replace an NT 4.0 server. I can browse my home folders, dhcp
works fine. When I go to join the domain I seem to have trouble finding it.
When I try to join the domain I get to the part about "providing a user name
with permission to create an account for the computer" I always get the
domain doesn't exist or it can't find it. My question is what am I missing?
i can't run an nslookup on the PDC but, should I be able to? I guess I need
some direction more than anything.
TIA
Tom