First, grab a arbrite cutting knife at your local home center or hardware store. You will also need a jigsaw with a good clean cutting blade,2" masking tape and a square. Use a square to mark the cut lines and score them with a arbrite knife. Then mask off with masking tape the cut lines and a couple of inches on the saved part of the counter top ( this protects the top from scratches left by the jigsaw base. Now remark your cut lines and saw away. Most drop ins have a lip that sits on top so you should have a little grace.