I bought the Broadcom BCM4360 AirPort card from Amazon for $30. It took about two weeks to arrive from China. I unscrewed my Macbooks bottom cover with my TEKTON 2830 set that includes the needed pentalobe drivers. The AirPort card should be easy to spot. I removed the screw holding down the card, and pulled the card away from the connector (Not the motherboard!).
After installing the new AirPort card, I booted up with OSX correctly identifying the card and connecting to my Wi-Fi network seamlessly. It connected to my router via 802.11ac at 878Mbps. It is not as fast as when my iMac would connect, but I am happy to be connecting at almost double the rate of the older 802.11n!
You can option-click the Wi-Fi symbol on your menu bar to get more information about your connection.
I am happy with the upgrade, especially for only $30! If you do a lot of local transfers or backups like TimeMachine and would like a speed boost, I recommend upgrading your AirPort card as well. Especially since it is so simple and cheap.