general problems of the 2012 GMC Sierra

Just purchases new 2012 GMC Sierra 3500 , 400 miles , have had alignment / steering problems with a drift to left and a wondering steering wheel, also brake and abs lights on, went to dealer they looked at it for 2 hrs, and said it needed a part ordered and there was a TSB on it, the tech said it would be safe to drive but I would not have abs brakes, also he would check alignment again at time when part came in 4 days est, brake and abs light remained on, vehicle drove fine the next day until a accident, went around curveat 55 mph, applied brakes to slow, brakes went to floor un able to slow at all went off the road lost control and crashed into trees, both airbags deployed , went to emergency room with arm injury and rib injuries, brand new truck very scarry I will never buy a gm poduct again.