About NAT and DNS behind firewall

Hi,
I am using windows 2000 adv. server NAT for internet.I also installed IIS server on my w2k adv server and published some sites on it.My clients are sharing internet through NAT and it's working fine.Now i want other peoples from my outside network can use it and also my internal clients.How i configure it so that other peoples can use it.Second i heard that DNS behind the firewall how i configure it on my w2k adv. server.
Anurag.