You want a wireless router, netgear, dlink, linksys, they are all good. And then as many cards as you want, I would buy the same brand as the router.
You want ones marked G or the new Double 108 Mbps. Just make sure the cards and router are the same.
If you want a firewall grab one with a firewall, most have that now.
When you get it home - unplug your wireless phone. You can plug it back in later, but it might interfere and unplugging it will remove it from the equation at least. If it does interfere, you want to change someones channel, but that is getting ahead of the game.
The other thing - RENAME Your router and add at least a simple pass phrase, most docs are really clear and will point this out as well. It is very easy to connect to somoene else's network or them to yours, but a simple password ends that.
It really is simple to setup and the documentation from those three vendors is really easy to follow. I would wait and look for sales. netgear just had a 1/2 price rebate sale.