When it comes to networking computers, I'm an idiot, so please help!

Right, I have an on-board NIC, which I currently use to connect my XBOX for playing online. To connect to the Internet, I have a USB Modem for broadband.

Now, what I want to do is take my XBOX downstairs to the living room and be able to play on XBOX Live, wirelessly.

I obvisously know that I'll need a wireless router, but am not sure which one, or which type to get. I'll also be getting a laptop soon, which is also another reason for why I want a wireless router.

What I need help on is just basically the hardware. Setting it all up should be ok, I'll be able to manage that.. As long as I have the right stuff.

So.. What do I do??