If your unit is like any Whirlpool dishwasher that I have repaired. the complete pump assembly is removed from inside the dishwasher. If the hose and wiring has been disconnected and the four square rubber
locks have been turned in toward the centre of the pump then you should be able to lift the unit up and out. Sometimes the rubber sealing to tub ring will stick to the tub and you have to be a bit aggressive on the lifting. Occasionaly I have had to pry gently up on the pump assembly from the bottom.