Burner valves are attached to the main gas line. When the switch is turned the gas then flows into a tube that mixes with air, creating the appropriate mixture for combustion.
Remove 2 screws holding the top burner. Remove 1 screw holding the electrode. Remove electrode from wiring using plier. Install new electrode and top burner
Remove the two screws from the burner assembly (on top of the burner). Lift burner assembly from the cook top. Disconnect the electrode wire from the electrode. Remove the screw holding the electrode to the burner assembly (on bottom of burner). Install the new electrode and attach the electrode to the burner assembly. Attach the electrode wire to the electrode. drop the burner assembly back into position on the cooktop. Attach the burner assembly using two screws.
This was VERY easy and I've never worked on this type of appliance before.
First, take off the grate, thermal plate, etc that are resting on top of the stove (this is all the stuff you take off to clean the stovetop).
Then, carefully unscrew the two screws holding the burner to the gas pipe. Grab the screws and set them aside so they don't fall back into the stove, then pick the burner up off the stove.
once you have the burner a few inches above the stove surface, wiggle off the single wire by grabbing it on the metal part (not by the wire) and gently wiggling it off.
Grab new burner, push on wire and sit it on stove, use a finger in the gas pipe to align it and put the two screws in. you're done.