Is this a twin oven and which one are you looking to replace?
Usually they are a light bulb inside a screwed on glass cover?
Ok, hold on
Not too tricky to fix. It is an 8w florescent tube 300mm by 16mm diameter.1. Turn off the power!2. Pull off the 6 timer knobs - they just pull out with a click. Leave the three big knobs.3. Slide the oven forward until you can access the back of the top panel.4. Undo the two recessed screws on the back of the extreme left and right of the top panel.5. Replace the tube, replace the front panel, push in the six knobs and set the timer.NOTE - the oven will not do anything until you set the time (including light you have just replaced)!