I'm buying a late 2013 iMac off a friend that came with the BT keyboard and Magic Mouse. My friend is keeping the mouse, as I have a Magic Trackpad and prefer it over the MM. I also have a wireless USB mouse to help me setup. Once the Trackpad is paired, I'm going to wipe the HDD and reinstall OS X. My question is after I wipe the HDD and reinstall, will I be able to use the BT keyboard and trackpad, or will I need a wired USB keyboard and mouse for the initial setup and re-pair the BT devices after?