2003 Ford F-150 Auto Headlights and door locks

My automatic headlights no longer come on during darkness. They do work by turning them on manually.
Here in the deep south it gets warm during summer and with having to leave the windows up when parked, I'm sure it doesn't do the interior any good.
If there is a dash sensor that controls the auto lights, could this be a cause? If so, how hard is it for a novice to get to it and change it?
The dealer wants $78.50 just to look at it.

At about the same time my auto door locks refused to lock once I have driven forward. They lock manually now but not automatically. Is this a related problem?

Thank you.