My iMac Intel 20" died on Christmas 2012. I never had time to repair it until today. I bought the power supply on ebay (a bit cheaper).
I took me one hour to follow all de instructions. A bit of a headache trying to attach the screen again, a bit tricky if your screw driver is not magnet (I used blue-tac in the end).
Now my iMac is alive, the power supply was different to the original one but same power and especifications.
The only thing is my screen have some issues with lines and color, I might not plug in the cable totally. One day if I am bored I´ll check it out.