Cadillac Repair: TWILIGHT SENTINEL, twilight sentinel, flat blade

Question
The interior and exterior lights on my '91 Eldorado all function properly however only manually.  I assume this to be a problem with the twilight sentinel and had questions as to replacement if necessary.  I've read it to be "child's play" to repair from photodiodes bought at Radio Shack.
Fact or Fiction?

Answer
Hi Laura,

      Replaceing the light sensor is really easy because it is mounted under a cover on top of the dash that is easy to remove useing a smaller flat blade screwdriver. Sometimes it turns out to be the module that goes bad but if you wanted to try the sensor then it might turn out to be a quick inexpensive fix.

    Let me know if you need anymore help. Bill