1999 Ford Contour lighting problems

I recently rented a 1999 mercury contour and drove it through rural western mass, vermont and new hampshire between dusk and dark, on interstate highways. Just after dusk I stopped to refuel the car. At that point the overhead dome light turned on, and would not turn off. I drove to the next rest area and stopped to read the owner's manual. It provided no useful information on turning off the light.

Headlights are clouding over, making it dimmer at night and harder to see the road ahead. I have tried to clean the plastic lens but nothing seems to work. I think this is a poor engineering solution when the car is only 6 years old.