A small feedback from my iman. (Late 2006, early 2007 20" display 2.16 intel core 2 duo):

Just changed my hdd and everything worked out fine. Two things are important as I found out that they differed from this guide:

1. In order to release the front bezel latches the card must be not be inserted vertically as shown in the pictures but with a slight angle using the direction from inside towards the upper corner of the bezel. I saw this in the following youtube video:

http://youtu.be/fOQ3joWnU-s

2. The torx requested to release the display screws is not a No 6 but a smaller one. Probably a No. 4, Ι am not sure exactly as I did not have one so I used a normal small screwdriver instead.

I hope I helped, the rest of the guide was very accurate and quite easy to follow.