DMZ and SuSE firewall

Hi to all. I'm planning to set up a demilitarized zone between the Internet and the Intranet. This is the first time I configure a firewall and feel a bit scared! :-) On between I will install a web/postfix server, and maybe plugging some more servers in the future. Of course, I want all computers on the Intranet to have access to the Internet with no restrictions at all. How do I have to configure both firewalls? Both should use NAT or maybe just one of them? Even better: Where can I find documentation about configuring such a scenario? (Please, not a 2000-page manual) Thanks in advance.