How do you change the EGR valve on a 1996 Toyota Camry?

It is simple. It looks like a little flying saucer and is in the rear of the engine on top near windshield. It was first described to me as one pancake with one pancake underneath & on top of it. There are two hoses that plug into it from the exhaust, and one coming out, and one on bottom (total of 4)