I was hoping that I would not have to unscrew the burner tops, the mounting screws for the two burners that are not working are totally rusted. Looks like that is a vain hope. I'm guessing the spark igniter is sandwiched between the cooktop and the burner, but I sure wish somebody would confirm or deny that for me.
Would like to know in advance what the screw sizes are so I can get some stainless steel replacements.
I like the idea of using vinegar to dissolve the rust, although I will probably use a stronger CLR (Calcium/Lime/Rust remover) hoping for faster action, since the client may not appreciate being without the stove for a day or so while the rust is soaking. In the past I've tried Liquid Wrench and PB Blaster with no success, even after waiting an hour for soak time.