[CentOS] A little iptables help

Wondering if anyone is willing to give me a little assistance with some
firewall rules. I think what I'm looking for is fairly simple, and I've
been trying to use webmin's firewall module without success.

I have a web server that I'd like to open up port 80 and forward a
specific port for a select number of allowed ips. That's it. Everything
else is dropped. 

allow: port 80
allow: forward port 8000 for x.x.x.x to y.y.y.y

Anyone willing to assist with the rules? And lastly, how would I apply
it in a way that it will always be in affect? If the machine reboots for
example.

Any help is appreciated. 
James