2008 Electical Harness for Door: speaker and light problems

We have noticed that when we listen to the radio or cd or DVD player that only the driver's side speakers work in the rear. We have played with the radio settings and if we move the controls to the passenger side we hear nothing. We have also noticed at night when we open the passenger side door the interior light comes on until the door is fully opened then immediately the interior light is off. I'm thinking its an electrical problem but I don't know where to begin. Is there a wiring harness that attaches to the door? Thanks!