The Pismo Airport slot is immediately adjacent to the cardbus slot and evidently shares its circuitry, but as has been said, it and the antenna are internal to the machine. Access is gained by removing the keyboard (though it helps to remove the little bezel above the keyboard/ under the screen too, which is easily done). The cardbus slot itself is thus left free for separate use. If you know what you're doing, it only takes about a minute to install, start to finish.

If anyone is looking for a good deal on an Airport card, by the way, the NY-based eBay seller electronicscafe has been intermittently selling them for $10 a pop (none presently), with very reasonable shipping. Best deal you'll find short of finding one lying on the street.