Switch off at wall and unplug if possible
Open the door or remove if possible
In the back of the oven at the top you will be able to see the end of the thermostat clipped in. You need to unclip it
Pull off the knobs and buttons from the controls. They maybe stiff but will come off
The oven is held in (or should be) by screws to the left and right hand side of the oven unscrew these and that will allow the oven to be removed from its housing.
Once removed you need to undo the screws that hold the top panel on and the back panel.
If you can access the screws that hold the thermostat in place unscrew them now, if not you need to remove the screws that hold the control panel in place.
Once you've removed all this you'll be able to see how to swap the thermostat with the new one.
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