Port forwarding works unless your modem, or ISP, gives you a private IP address. Then you have more work to do. If it's your ISP you're probably screwed. If it's your modem, there is a way to change it. Just have to figure out how.
@Beast. Give your Wii a static IP address. Your router will have a DMZ option. Most of the time you just have to check a box to turn it on and then add whatever device's IP address you want to be outside the firewall. In your case, the Wii.
My problem is that my router isnt on the web anywhere, and were the netgear/linksys walkthroughs show you screenshots etc, there arent any for my router, and the stuff the others have arent on mine, like tickboxes for dmz etc.