[Samba] Samba, subnets and DHCP

[melter]

Hi!

I have planned following setup:
I have got Linux box with two ethernet interfaces (connected with
bridge) and samba and iptables. Behind the first interface is the real
world and the other is my own LAN with variable number of workstations.
All computers get their IP address via DHCP and I use dynamic DNS on
some machines. Machines could get IP address in same subnet or not. My
questions are:
1) How to set up the Linux box so that I can use machines behind the
Linux box as there is nothing between the workstation and internet? This
question is possibly in wrong list... :-)
2) How to set up samba so that I can browse it and all workstations in
my LAN can "see" each others?