Servicing an older wall oven

Long-shot question here. We have an older (1970s?) Magic Chef wall oven that needs servicing. Reliance Appliance can't do it, and I have been having trouble getting in touch with Henry Rutgers, whom others have recommended. We need help! Can anyone recommend someone who would at least be able to, like, take a look to figure out what is wrong with the oven, clean lines and burners so stuff lights properly, etc.? (We are trying to avoid replacing entirely, as we rent, and the landlord's approach would be to tear up a bunch of cabinetry and wall to replace the stove, which is a whole other can of worms.) Thank you!!