The dishwasher overflow was not put back in. Is it necessary to have it? If I need it I will have to call and have them bore a hole in the granite to be installed.

That is called an air gap, not an over flow. It is designed to stop any chance of your drain siphoning dirty water back into the washer. It is code in many places but most of us would tell you to make a high loop with the rubber drain line from the washer. Run it up to under the counter, secure to top of the loop and then drop back down to the sink drain connection.http://www.diynetwork.com/videos/dishwasher-high-loop-hose-video/33822.html

STOP!! Don't drill that countertop! Follow Bobs advice and install a high loop,(seer image) air gap instead. Counter top air gaps can and do fail while we have never had a complaint on a high loop system. Good luck, Tom

Check with your Inspector first. In some areas it is mandatory to install. Otherwise, follow Bob's and Tom's directions. Back to you. Milo