1996 Plymouth Voyager Check engine light.

Computer problem
1996 Plymouth Voyager 6 cyl Front Wheel Drive Automatic

Hello my name is Eric. I am a quadriplegic and I am not able to do things myself. My question? My service engine light/ check engine light came on. I had my daughter check the oil. She said it was a little dirty. And it was just below the full line. Does the light come on if the oil goals below the full line or if it's dirty. That's my question Sir. Thank you very much, Eric. Also what kind oil does my engine take.