yes WEP works with the existing card.
The existing card is typically a Cisco Aironet 350, which its firmware has severe problems with WPA, as the card was designed before WPA became standardised.
If you wish to replace the card, You need another type of card with antenna couplings that can fit in the PCMCIA slot with nothing sticking out past the top of the slot, there aren't many like that.
-Thom