This is the orginal thermostat which was difficult to set. I removed the screws from the black face plate.
The next step was to drill out the rivets that held the thermostat in place
Next step is to remove the wires from the thermostat.
I connected the wires to the back of the thermostat, Screwed this to the black face plate and reattached the face plate.
The new digital thermostat. Note I am going to add some spacers behind the thermostat to make it easier to replace the batteries.