Step 1: Ditch the Timer!
Step 2: Gather Your Weapons
You may have some specialty fasteners that will need a special torx tool or you can just file down the pin that is in some of the screw heads otherwise basic tools are all that is needed.
Step 3: Open Says Me
First unplug the power box if you haven't. Remove the covers and timer and mark the connections. I like to use color coded wire caps.
Step 4: Location Location Location
Pick a spot on the box exterior that will accommodate the mounting of the light sensor and not interfere with the internal components of the power box. I like to use painters tape to keep perspective of my measurements so I don't make too many mistakes.
Step 5: Drill and Fill
Drill the hole that will accommodate the sensor. I prefer the use of a hole saw but sheet metal snips can be used as well. Attach the sensor and connect using the instructions that came with the sensor.
Step 6: Assemble
Put things back the way you found them minus that pesky timer. If you have junior scientists/explorers living in your territory you should consider adding a screw to lock that lid down and prevent shocking life lessons from occurring.
Step 7: Fogeddabudit
Remount the power box and aim the sensor toward the source of natural light. That's it. Now it should go on in the dusk and off at dawn. Fin