I knew the hard drive on my 27" iMac was beginning to fail. It was getting slower, programs took longer to load, it was just a matter of time before it went belly up and died. Decided to be pro active and research what to do and if I could handle the repair myself.
The repair went well- looked over the tool list and had everything setup and ready- the entire repair time to do the replacement took about 45 minutes- just stopped several times to review the repair list which I had printed out and loaded on my iPad for reference :-)
The most difficult area for me was the vertical sync ribbon cable- you need to have tweezers for the removal but it takes patience for the reassembly of this cable because it is your final part to connect. I had to have my husband hold the display up so that I could work the cable back in place. It actually took me a few times to get it locked back in place. You just need to make sure you have it turned correctly so it slides back in snug.