kitchen aid superba range problem

Hi everyone,
I have a KitchenAid Superba range which has the electronic control for the oven. See pictures at:
http://members.shaw.ca/plz/kitchen_aid /
The problem is that only some of the "buttons" on the control surface work. For example, the Start and Cancel ones don't so I can't use my oven :(
Some of the buttons do work but not the critical ones. This has only started recently. I know there are two parts that are potentially at fault.
1. The glass control surface and the sensors underneath it (it's all one piece). 2. The circuit board that controls the inputs from the glass control surface. This board is below the glass control surface and is connected to it.
Needless to say both these parts are quite expensive. I would like to diagnose which of the two parts is faulty and replace the part. Would like to avoid replacing both if they are not both bad. I have a multi-meter and am comfortable with diagnosing electrical issues on my cars and motorcycle. But I don't really know how to tackle this to pinpoint the cause of the problem. I think the sensors in the control pad are capacitor based but am not 100% sure.
Does anyone have ideas on how to figure out the cause?
PS - I have had the control panel off in the past to replace one of the stove top controls so no problem with disassembling the range to get at the parts in question.
Many thanks for any information.
-Peter
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