Below is the link to your router and it does have a firewall in it. It is actually a Linksys Wireless Broadband 802.11b
http://www.networkeverywhere.com/products/nwr04b.asp
Your router supports UPnP but I can not find instructions on enabling it. But below are instructions to port Forward it. If you port forward you must set up a static IP address.
http://portforward.com/english/route...B/Limewire.htm