You will need a 10mm socket and an inverse allen wrench set.
To start, you will need to remove the four nuts holding the Regulator to the body
You'll notice there are grooves along the Pressure Regulator / Control Unit's switch. The larger grooves need to be lined-up with the nuts in order to remove them.
Remove the pressure assembly. Using the allen key, remove the poppet from the assembly. The poppet comes in three pieces, the internal screw may be difficult to remove. If so, the kit comes with a new screw and poppet.
To complete the repair, place the seat back on (flat side down). Next, replace the poppet. Then, replace the screw. Make sure to tighten it until it is flush with the poppet.
Optionally, you can place the poppet seat in the o-ring. Just slide the o-ring over the poppet seat. To install, push out the old poppet seat from the bottom side of the Regulator. This is an optional step!
Reinstall the pressure switch, making sure the switch and the gauge are on the same side.
To finish the repair, tighten all four screws.
Watch the companion Insructional Video to see how this repair is done: