I just started using that exact notebook about 2 hours ago. It's my new work laptop. It seems decent so far. Small, light, relatively powerful and a nice screen. Haven't tried the Wi-Fi yet, but the Dell AP that you recommended just arrived yesterday so I'll give it a shot this weekend. Don't know anything about replacing the existing Wi-Fi card, but two thoughts:

1. The built in Centrino is only 802.11b, as you probably already know.
2. There is a PCIMCIA slot on this machine. Just one, though.

FWIW,
Jim