You wont have to worry about the laptop, it will be wireless ready when ever you decide to purchase. There is no other fees to pay at all, just buy the wireless router and set it up.
The router will be able to connect up to 4 computers wired, and as many as you want wireless from one internet connection. Just plug the wire from the modem to the router, then from the router to your desk top pc. The security is important! You dont want people coming along and downloading from the internet off of your internet connection. The installation is very simple and straight forward, and you should be able to set it up in a few minutes.
You will enjoy being able to connect to the net from anywhere in your house with the laptop, and also when traveling. Most motel/hotels, fast food, starbucks etc have a wireless connection for its customers.