The Wlan card is connected to the miniPCI port on the motherboard and it’s possible to remove/disconnect the card.
But there could be still an compatibility issues between new device (Wlan chip) and the BIOS.
I read here in the forum that someone has replaced the Wlan card and finally the notebook didn’t boot up due to the compatibility problems between the Wlan and BIOS.
So in your case I recommend using an external Wlan solution.
The WLan stick is easy in use and should be compatible with most systems.