Yeah, it would take some work. I do know that on a Dell Latitude D-series, the antennas are attached to the side of the LCD panel with screws.
That being said, the card should work with only two antennas connected. However, that will cut down on the maximum supported speed of the card, since each antenna (and radio attached to it) allows for a connection up to 150 Mbps. Without the third antenna, the maximum speed the card will connect at is 300 Mbps (150 Mbps for each connected radio).
Casey