How many miles on the car? How many miles on the oil when the check engine light came on? Where was your temperature gauge when the light came on? Normal? Had you been doing a weekly under hood fluids check and walk around check? My hypothesis is that your oil had gotten really low and that the leak may have been at one of the cam covers. (They are not valve covers on an overhead cam engine.) Had you noticed any oil on the ground where you normally park you car in the weeks prior to your Armageddon? Did you ask the mechanic how many quarts of oil came out when he removed the drain plug? Don't bother!! They just pull the plug and then raise up the catch can funnel and could care less how much oil came out. They start their "free complimentary 26 point inspection" while the oil is draining. I believe that if my hypothesis is true, you were running your engine extra hot for some time prior to the Check Engine Light popping on and that therefore you have severely stressed your engine and that multiple failures will now begin. You've already had the first one - the water pump seal. Best check your oil at least once a week to make sure it hasn't turned "coffee with milk" color. This indicates a head gasket failure which is sure to come if my hypothesis is correct.