How to fix Rangemaster 110 switch for left hand oven?

Moved into new house that already had Rangemaster 110 - the previous owners didn't tell us that the left hand oven doesn't work. It feels like the switch just doesn't engage at all and the light doesn't come on when you turn it. Is this something I can repair myself? We contacted Rangemaster and they quoted us a ridiculous amount just to come out!