Problems with Whirlpool Ikea fan oven, switching itself off?

My Whirlpool Ikea electric fan oven has been acting strange lately. Firstly if cooking over 200c for any length of time it will switch itself off, this seemed an intermintent fault.
Now the light on the control panel that should go off when up to temperature doesnt come on at all, but oven does get hot. Also when you turn it off by the control knobs, the fan blows continually and the panel doesnt show the time.
I'm willing to open her up to fix things, just need to know what to replace first and if the costs are justifiable.

Thanks in advance.