I bought a new GE dryer today. I attached the 4-wire power cable per the directions, plugged it in, and it works. But, the top became really hot really fast. This can't be right, so what's wrong?

Be sure the air vent duct isn't obstructed. Air must pass through the machine to carry out heat and moisture.

The ductwork is probably too long, folded over on itself and it is plastic. It worked on the old dryer. I read in the manual that it had to be metal. Is this true?

It's a fire hazard issue. Aluminum flex duct hose is available and cheap.

OK, so I put on a new aluminum exhaust duct, and it's still doing it. Even when it is not running. So, is it the electrical cord? I installed it per the directions. However, the dicevctions didn't specify what color of 'hot' wire go where. Does it matter if red is on top or bottom?

Somewhere there is a "direction-of-rotation' arrow, or something to tell you if it's running backwards. If it's not rotating in the right direction, try changing the red and black wires on the plug.