This car is OBD compatible most parts stores like Auto Zone can do free code reads. If you can get me the code number I can better advise you. If the car is otherwise running normal 80% of the time the malfunction that trips the light on is usually related to an emissions failure such as a loose gas cap. Since you have a flashing light this means there is some type of misfire that can damage the converter. Can you get me the code numbers? Did you dry the spark plug tubes out?
If the car was only down 2 quarts there is not likely any damage. If they did no oil change it should not be leaking engine oil. Did you check the oil in the engine before going in for the power steering oil leak? Was the vehicle using oil prior to this repair? The running run is probably due to the plug wires being wet.