Karcher Pressure Washer 620M?

I have had the above machine since Jul 2000. The on/off switch on top of the unit is not working properly, and only after several attempts does the motor come on - stop it/restart - go through the same procedure. Basically is the stop/start button knackered and in need of replacement. If so I can obtain a new part through eSpares - need a torx screwdriver set to take cabinet off. Is this a simple job?