Is it safe to cook in a grill\oven that is rarely cleaned? I don't grill or oven often and there always seems to be dirt and crumbs left over from long ago.  it's a mammoth task to clean so i dont clean it.  i just think provided the food sits on foil paper and doesnt make contact with any of the previous food and i dont eat the previous food all should be well.  the heat should also kill any bacteria thats been there for a long time.

is eating food in above situation safe or not?

Just to add following peoples request for more information, it is not just the crumbs i'm concerned about.  though it hasn't been used the walls inside the grill(broil) compartment look sludgy and touching the walls sometimes reveal sludgy dirt.  the oven is at least 20 years old so might have something to do with that.
The build up on the oven walls is likely grease.  

Food contamination risk is low to none if they don't touch.  

The bigger risk is a grease fire.