I just finished replacing my hard drive following these instructions and they were perfect. The only minor complication involved the ribbon cable connecting to the sleep light and IR sensor connectors. The entire cable was tightly glued to the hard drive. But I got it loose with 10 minutes of gentle prying with a spudger.
To keep track of the screws I just sketched an outline of the bottom panel, taped the screws in the right places and numbered them with the step numbers.