My Pro 17 turns on but won't turn off. Does it need a new switch?

That is a continuous feed model and has a switch mounted in the ring where the lid fits. They are prone to getting gunk and rust in them. Sometimes you can spray WD 40 in there and it will free up. They are expensive switches and I personally do not recommend this series for that reason. I usually install a Badger unit at 1/2 the price.