Whirlpool built-in double oven; top not heating
 

I have a double oven that is about 6 years old. the top oven recently quite working. It will turn on and sounds like it wants to start the pre-heat/warming process but it never gets hot. From my prilimary research sounds like it could be a thermal overload switch. Any other thoughts before I purchase that part. Also, how difficult is that to replace in a double oven? Thanks for your help.
John