My 2004 iMac G5 1.8GHz machine came on for a moment, then went off. What the ???? Did a search on the net (with my trusty MacBook Pro) and found that this was a common problem with iMac power supplies. Hmmm. Where to get a replacement power supply, I ruminated to myself silently. iFixit! Yep, the reason that I even decided to do this job myself was because I watched the video of the young lady replacing the power supply in an identical iMac. She had it fixed in no time.
No joke - From the time I got the iFixit replacement power supply out of the mail box till the time I was back to surfing the web on the iMac was 17 minutes. Could not have been easier. The video of your tech replacing the PS was spot on. I found that the spudger was a handy device.
As with any computer repair, remember to unplug the computer from power and place the palm of one hand on the computer chassis as you work, especially in dry and arid locations as the static monster can come and ruin your day before you know it.