Hi guys, Just picked up a replacement 512gb SSD for my mid-2012 macbook air 13inch. Seen a few vids online explaining how to swap it out however I have a couple of questions. I know need to back up to an external HD and then swap out the SSD. But what do I do from there? Do I need a back up of the OS on a usb? If so, where do I get that from? Or do I simply plug in the external HD and boot back in from there? A video or step-by-step instructions would help.. Thanks.