2009 GMC YUKON XL Engine And Engine Coolingengine Problems

WHILE DRIVING FROM GA TO LA ON CHRISTMAS EVE, MY YUKON XL WENT INTO REDUCED ENGINE POWER AND LOST TRACTION CONTROL AND ANTILOCK BRAKES. THE CAR ALMOST INSTANTLY DROPPED FROM 72MPH TO 45MPH AND THE CHECK ENGINE AND TRACTION CONTROL WARNING LIGHTS CAME ON. I WAS ADVISED BY ONSTAR TO PULL THE CAR OVER AND TURN IT OFF FOR A FEW MINUTES. WHEN I STARTED IT AGAIN, POWER WAS RESTORED, BUT THE CHECK ENGINE WARNING LIGHT REMAINED. I WAS ADVISED THAT THE CAR WOULD PROBABLY DO THE SAME THING AND THAT I SHOULD HAVE IT SERVICED IMMEDIATELY, ON THE NEXT BUSINESS DAY, WHICH WAS MONDAY DECEMBER 27TH. WHILE DRIVING TO A DESTINATION ABOUT 30 MILES AWAY ON SUNDAY, THE CAR WENT INTO REDUCED POWER AGAIN AND THE WARNING LIGHTS RETURNED. THIS TIME TURNING THE ENGINE OFF FOR A FEW MINUTES DID NOT HELP AND POWER REDUCTION REMAINED. I TOOK THE...