Jenn-Air Wall Oven Won't Heat

I have a Jenn-Air electric wall oven, model W131W. Oven will heat but not to the indicated temperature. Replaced the oven sensor, did not make a difference. Oven elements are heating up (red when heating), but does not reach the indicated temperature. I have to increase the oven temperature by 100 degrees to get the required baking results. What else should I replace on this oven?

The door on my microwave oven Is cracked just below the handle and along the side where there are three screws. I would like to order a replacement part ,but not sure what is the correct part.
How do you remove the door and how do you remove the the outer frame?
Thank you in advance for your help.