Dealership is opening my dash up again

to prove they changed an evaporator core for me. All signs and parts paperwork lead me to believe they changed the heater core instead.

How can I tell when I view it which part is the newer one? Numbers? Anything? Obviously I will look for "newness" but the car is only 2 years old.

Also, how can chemical odors be removed from HVAC sustem? They used a strong chemical which I am sensitive to. Inwas going to bring in a non-smelling soap. Would that work? Can sustem be "flushed" somehow to get the odor out?
Thanks