Sounds like the main oven element is gone. Never worked on your type of appliance but generally there is a plate at the back of the oven ( usually where the fan is situated ), held in place by a number of screws. Remove this plate and you should see the element. Again the element is held in place by some screws, undo them, element lifts away and and then you should be able to disconnect wiring. Fitting new element is reverse of above process. Hope this helps.
Donnie at Skyeline Services, December 2005