Simpson Evolution 808 oven made in Australia in 2000. Almost all ovens made in Australia by Electrolux (Westinghouse, Simpson, Chef, etc) in the last decade or so use a very similar design so this instruction will suit.
I was half way through cooking a pizza when my safety switch tripped off the power to my house. I flicked it back on and all seemed fine ... until I came back to check on my pizza. The oven temp had dropped to almost nothing even though the fan and oven light were still working. So rather than buy a new oven I figured I could fix it.
All I needed was a phillips screw driver, a small hex socket drive and an 8mm spanner.
1. Turn off the mains at the switch board. There might be a switch near the oven or stove too, turn that off as well. Check that the power is off!
2. Remove the screws holding the oven to the cupboards. Mine was held in by 4 timber screws on the edge.
3. Slide the oven out of the wall. I used a small table to support it.
4. Remove the hex drive screws that hold the top lid on.
5. Using a trusted multimeter CHECK THAT POWER IS OFF! There are now exposed power terminals.
6. Undo the supply power terminals and remove the cable. I taped mine up.
7. Remove the back cover - more hex screws.
8. Pull the spade terminals off the heater element.
8. Inside the oven remove the shelves and side racks. They pop off the wall.
9. Pull the rear fan shield towards you. It should pop out at the top and then lift off 2 small tabs.
10. Remove the phillips screw at the bottom of the heater element.
11. Remove the 2 spring clips.
12. The element can now slide down and towards you.
13. Replace the element and put it all back together in reverse order.
I bought my spare element for $66 from Statewide Appliances. They said it was an extremely common part shared by lots of ovens.
Hope that helps.