Begin by disconnecting your Mac Pro's power supply and any other devices currently connected your Mac Pro. Remove the side panel of the computer. Your Mac Pro should appear as in Figure 1, with the Wifi card (top) and the Bluetooth card (bottom) near the main fan.
Begin by removing the Bluetooth card. Using a small screwdriver remove the screw in the bottom left corner. Directly above the screw you will see an antenna wire (black with a gold head) connected to your Bluetooth card. Pull it lightly towards yourself and it should disconnect from the Bluetooth card. Make a mental note that this antenna wire has a tag with "BT" on it, indicating it is the Bluetooth wire. You may now pull the card out and set it aside.
Look at your current Wifi card. On the left side you will see three more antenna wires similar to the one that was on your Bluetooth card. Detach these by lightly pulling on them. Use the same screwdriver from earlier to remove the two screw directly above and below where the antennas were connected. Once you have removed the screws pull the card to the left, removing it from its port and set the card aside.
Grab your new Wifi and Bluetooth card. All of the antennas that you disconnected from your previous cards will need to be attached to this card. It can be difficult to attach the antennas properly; be patient and do not use excessive force. The Bluetooth antenna wire (marked with the "BT" tag) should be connected to the port marked "J3" on the card and in Figure 4 with green*. The other three antennas may be attached to any of the three remaining ports. Once all the antennas have been attached slide the Wifi and Bluetooth card into the port. Push the card flat against your Mac Pro's Logic Board and use one screw to secure the card in place. Installation complete! You may now reattach your other devices and the Mac Pro's power supply.
* Some of the cards we ship have the ports on the back side of the card. You should still connect the Bluetooth antenna wire to port "J3".
If you also use your Mac Pro to boot into Windows be sure to download the Boot Camp 5.1 drivers from Apple. Once you have completed the download install the Broadcom drivers included in the package while booted into Windows.