Appliance Repairs Job - White River, MP, 1240

I have a very old Defy 600S oven. The oven was not working so I replaced the thermostat. Oven is still not working so assume it's the element/s in the oven. I have tried to remove the element but the screws are so tight I cant get them loose. Do you still repair such old ovens and is it worth repairing the oven? If it is worth repairing, can you please quote me on what it would cost to repair it. Thank you.