I have a Delonghi double oven model nds 1350. The bottom oven doesn't work on the regular oven setting. The other functions work in the bottom oven. Seems the selector needs to be replaced. Went to the shop a was asked how many contacts does it have?? Also how do you open the stove top to replace the selector?? I removed the 2 screws on the side and back but didn't lift off??