Colud the shop possibly have messed up the head gasket???
check the coolant hoses for the egr cooler that go into the fire wall
Check the rubber O ring just above the thermostat. (It is around the black coolant pipe where it comes out of the engine to go to the radiator) I have replaced mine a few times.
take it back and make them fix it
There is a plate on the block behind and below the headgasket under the up pipe. It's about 1.5" X 4".