Hotpoint WD440 fault?

The machines on/off switch works ok, but the start/cancel doesn't seem to have any resistence and it won't start.

I have had a look inside & taken off the PCB. All of the external buttons match to a button on the circuit board, except the start/cancel button. It looks as though there should be one & it's fallen off.

Is this the correct assumption?

Secondly, if I attempt replacing the PCB myself, anything particular I need to be careful of?