problem getting clients to see server/join domain

I've just set up a new 2003 SBS server that is hooked to a DSL modem on
one NIC, and a 7-client network on the other.

Upstream NIC has its IP address and DNS server set by DHCP.
Downstream NIC is set to 200.100.30.30 (though I've been advised to use
192.168.16.X)
DNS server is set to point to itself and has the ISP's servers set as
forwarders.
Clients can receive IP addresses from the server's DHCP.
Clients point DNS to the server.

Yet the clients can't join the domain, nor browse the network and see
the server. And this being my first time setting up a server, I need a bit
more detailed help than most. Any help you all can give would be most
appreciated.

Also, when a client joins the domain should it be entered as
"server.domain.local" or "domain.local" or just "domain"?

I just recently set up a two office system and am still in the process of making it more secure

I found that if from the server management console. click the computers icon, then setup client computers, follow the wizard, and make sure you have the computer name from the desktop computer (properties of my computer, computer name) enter the computer name, check the programs you want sbs to load on it, when you are done it will tell you to goto the client computer and type in an address. ie: server.connectcomputer, or something like that,, just follow it and you should be good to go, it will set up everything from there, including exchange if you have it installed and running
feel free to contact me if you have any questions im here from 9-5 eastern mon-fr

good luc
(E-Mail Removed)