I bought an Imac 24 on the Swedish ebay "Tradera" guessing that there was a problem with the power supply. Thanks to the guide here on ifixit I thought that I give it a try so I ordered a new power supply, 3 screwdrivers and suction cups.
Thanks to the guide on ifixit i managed to replace the power supply in half an hour. I was very excited when I first pressed the power button and I could here the apply startup sound, however, the power supply was not the only part that was corrupt. The hard drive was also bad so I had to take the Imac apart one more time to replace the hard drive (had one 1 TB laying around).
It is a good idea to be 2 persons doing this repair. If one can hold the LCD you don't even need to disconnect the LCD. That will save you some time.