You remove the PCB and wire straight to the switch!
You need to strip it down quite far, but basically:
Undo the 4 outer screws, flip back over and lift the hat off. lift out the cord rewind unit and remove the little wheels (or watch if they fall out
Pop the cover off that covers the switch and wires behind the switches and unplug everything.
Flip back over and remove the 3 inner screws, then pull the (now top, was bottom) off.
You'll now see the PCB, remove all that and it's wires. You will be left with the L&N from the cord rewind, and 2 white wires from the motor.
Put the bottom/top on with the 3 inner screws (I fit the sound deadening inside the case thing then slip that over the motor, then place the motor rubber on top)
Back to the wiring, and wire the L&N to one side of the on/off switch, and the 2 white wires to the other side
Leave the hi/lo switch in if you don't want the hole
Plop the cord rewind in
fit the top cover
try it! You should easily see if the motor has blown when you get to it in the usual way!