you can do this all quite easily.
at least, i found it easy in gentoo.
gentoo.org/doc/en/home-router-howto.xml
paste that into address field & it'll work.
since this is my first post i couldn't link to it; sorry.
you could probably adapt it to your needs.
basic steps are
- get network card drivers and network options into kernel
- connect to outside world
- start/configure network and services for inside world
- NAT ( gateway to the internet for your computers)
- port forwarding (forward required ports to windows)
you could simplify it (at the expense of security) by setting up the firewall to accept anything. that would remove the need for thinking almost entirely.
or you could just follow the howto which is pretty simple.
you don't really need dns or dhcp service - for help replacing w/ static configuration, just ask here! it's easy.