I needed to find a tiny star head screw driver and used a regular Phillips screw driver. I made a diagram of the 5 terminals that had wires connected. Removing the old timer was simple. Just remember that one notch needs to be depressed for turning the timer to pull it out. The whole job took less than 30 minutes! This was based on not having done this before. A pro could probably do it all in 10 minutes. It's that simple! Note: The timer diagram and part number were in the cavity holding the timer. I expected to find it in the manufacturers instruction manual! Other than that there was no mystery involved in replacing it!