500 GB hard drive was slowly failing. I restored the system to an external HD. Then I used Disk Tools to erase the internal disk and write zeros; that apparently caused a fatal failure, so I knew the disk was bad. I used the ifixit repair guide for the EMC 2210, which is quite detailed.
Successful. I opened up the imac twice. First time, I replaced the HD successfully with a new 1 TB drive. About 3 hours from opening up to putting back the glass screen. ( I took time to vacuum and use canned air to remove the dust inside. I was relieved to see how easily the glass came off using your suction cups.) However, as the computer warmed up, the fans started running continuously at full speed. Using the Apple Hardware Test, I got the error code:
Your guides are very good and seem very accurate. On my imac I found that the Phillips #1 didn't remove the access door covering the memory slots. You need a #2, and that is what my "Everything Mac" manual indicates. But the center point of the screwdriver cannot be too long, or the Phillips blades will not gain purchase on the screw: its center depression is shallow. It would be helpful to have a full picture in your guides showing the inside after removing the LCD screen, indicating the relative placement of the drives, boards, power supply, etc. Here is one I took of mine.