Check out this link to a user manual that helps to describe the location of the retaining wire:
http://shared.whirlpoolcorp.com/assets/pdfs/literature/Use%20and%20Care%20Guide%20-%208113P625-60.pdf


1. When oven is cool, hold bulb cover

in place, then slide wire retainer

off cover. NOTE: Bulb cover

will fall if not held in place

while removing wire retainer.

2. Remove bulb cover and light

bulb.

3. Replace with a 40-watt appliance bulb.

4. Replace bulb cover and secure with wire retainer.

5. Reconnect power to range. Reset clock

I hope this may help you if it doesnt have visible screwss etc.

Sometimes the glass lenses are held in place by clips behind them which are not visible.
I am not familiar with your machine but I suspect the lens in thick glass and is slightly 'proud' of the oven side.

You have to have faith that it wont break it, but you have to CAREFULLY lever the lens out of its fitting using something like a blunt screwdriver. Once you get one side started, you will get the idea. The bulb is right behind it.