I agree with redline, be sure to print out the screw guide and put double-sided tape on the lists of screws. That made it very easy.
Be sure that you have the proper size screwdrivers and apply signficant pressure while turning the screwdriver slowly --- several of them seemed like they would strip very easily. Beware of the screws in the battery compartment, they are somewhat difficult to access and very tight.
This is a very worthwhile project -- I took our lab iBook (that no one wanted to use because of the small, old harddrive and simple CD-ROM) and swapped in a better HDD and optical drive, now the students fight over it.
good luck,
JT