Excellent guide. The entire process took less than 90 minutes and I was not in a hurry. Everybody told me that the iMacs were designed to be "user-proof" and had to be worked on by qualified technicians. What do they know? Now my computer is back up and running with a 1TB drive and it cost less than $150 - even with shipping costs factored in. Great job guys!!!
I could not get the LCD power cable disconnected from the board - it is on really hard and there is no way to leverage it off without breaking something. My solution was to leave the screen attached and rotate it away from the work area/computer (granted you need a work surface that is large enough and a soft surface to place the screen on). If you try this method, be careful that you keep clear of the screen during the remaining steps - should not be hard.
It seemed that if I ever got the connection unplugged, there would be no way to get it back under and re-attached properly.
This is probably the toughest step of the entire process that needs a workaround.
When they assembled my imac, they forgot to put the two torx screws in. Saved me about 10 seconds. The cable was quite secure and easily popped on and off.