Purchased Slide-in Range and installed summer of 2002. After nine years, noticed the smell of gas when setting oven and that it didn't light immediately; occasionally, not at all. Eventually, the oven stopped lighting. Am able to light manually, but there have been times when it would not. Broiler works, stovetop burners work. An element in the rear of the oven glows when oven temp is set. Would it be the igniter, the sensor . . . ?