After what was a slow and eventually stalled update I finally got the system running again. But I booted up today and ten minutes into work my second monitor cut out. I am afraid to reboot because others have had their displays disappear. I have major thunderstorms headed my way in the next 3 hours and I need to find out how to uninstall the update before they get here. I am somewhat new to Mac and this is the first update for me so how do I do this?