Looks fairly easy to install where I just took the old one out. But
the old one has two wires coming into it, one black, one white. The
instructions for the new one (hasn't arrived yet) shows three wires,
with the third one attaching to a screw on the dishwasher's electrical
box.

Since I only have two coming up from the house panel, can I just run a
wire to something that should be grounded, maybe the drain pipe?