If you get a router you should just be able to plug it into your modem, and your PC (after getting the wireless adapter, which you will need; these can be found fairly cheap) and Wii should both recognize the signal. Read the instructions that come with your router and follow the steps under wireless connection in Wii settings, it should be an easy setup process. You will of course also have to reconfigure your PC settings as well for the new connection, but if you have ever done this it should also be a breeze. This is the best way to connect to the internet for your PC and Wii hands down.
There should be an ethernet or maybe a usb port on the router. Plug the wire from your modem into the router and go through the setup processes (you should put the wireless adapter into your PC where you take out the wire that goes to the modem, unless this is ethernet; the wirless adapter should go into a usb port on the back of your PC). You should be connected to the net with both your PC and Wii in no time as long as this router works, which it looks like it will.