Step 1: the first step in taking out an old dishwasher is to remove the access panel below the main door. Look for a couple of screws on both ends of the panel that, when removed, will free it from machine's framework.
Step 2: once the access panel is removed, loosen the nut that holds the water supply tubing to the machine using an adjustable wrench. Place a bowl under the tube to catch any water that may drain out. Also, remove the electrical cable.
Step 3: Once the water and power connections are removed, the only things holding the machine are two screws driven into the underside of the countertop. These are usually located at the upper corners of the unit. Remove the screws.