Port Forwarding for RDC connections.

I could use a little advice here… I have an xServe running 10.2.8 and is currently our NAT/Firewall/HTTPserver/FTPserver/FileServer. Ihave a second server on our local network that is running Terminal Services on an Win Server 2003 box. I had to set-up the firewall/nat by hand as Apple didn’t supply good enough GUI tools. So here is what I want to do… I need external users to have the ability to use RDC to connect to the TS server. How do I set up port forwarding and edit the IPFW?

our xServe via en0 – 75.xxx.xxx.xxx – forward port 3389 tcp + udp traffic to an internal server 192.xxx.xxx.xxx via xServe en1…

Thanks for any info!