I have a Linksys router, though not the same model (nor a wireless one). I have a static IP address for one of my computers, and dynamic for the others; that's likely what you want. Go into your router's config and enable DHCP. That will cause your router to give out dynamic IP addresses to anyone who asks for one. There should be a setting like "starting IP address" which is the first IP address your router will give out via DHCP. Set it to 100 or something like that, so that 192.168.1.100 will be the first IP given out via DHCP. On the computer you want to have a static IP address, set it up NOT to use DHCP, but to request an IP that's below 100, for example 192.168.1.2. Use something like IP 192.168.1.2, broadcast 192.168.0.255, netmask 255.255.255.0, gateway 192.168.1.1 or whatever your router's IP is. (Those are the settings I use, yours may vary.) Your router should happily give it to you. Then you just have to set the router to port-forward to 192.168.1.2 and you'll always get it there.

Don't just disable the firewall. Hardware firewalls are you friends. Be careful forwarding ports too. I can't imagine why a game would require port 80 or 443; I assume you're running a web server? Just be careful.