|do I need a seperate wireless card if I buy a wireless usb adapter?|
You don't need both a wireless card and a wireless USB connector.
Does it matter g/b/n? I'm a bit confised.
What is your router? It will most likely be B/G. If it's also N capable, I would get an N adapter. To be honest though, it shouldn't matter as any adapter you buy should be backwards compatible with previous versions. So, if you get an N, it should also do B/G but before you buy, verify this.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.