Ouch!
Well i've got some good news you don't need to take the display assembly apart only take it off as the antenna unit is within the clutch cover (black plastic between the hinges. Here's the IFIXIT guide to get the display assembly off: [guide|23392|MacBook Pro 15" Retina Display Late 2013 Display Assembly Replacement]. Then get this part: [http://www.thebookyard.com/product.php?manufacturers_id=17&products_id=12547¤cy=EUR|iSight Webcam WiFi Cable Apple P/N 818-2882]. The trick here is to carefully unsolder the antenna lead you need and feed it though the hinge replacing the broken one.