well, all i can say is this:
shut down laptop, ground yourself, flip it over, unplug the power adapter, take out the battery.
you open the laptop with a torx 8 screwdriver.
once unscrewed pull the lower casing up and towards the front (cd side) of the laptop. set aside where it won't get stepped on
the hard drive is in the center under the trackpad
unscrew the one screw near the front (cd side) middle of the laptop. it is the screw that hold down the plastic part that separates the battery compartment from the hd. there are two, one on each side of the front of the hard drive (actually, the lower left and right corners, going by the label on the hd. remove the lower right one) removing this screw will give you a little extra maneuvering space.
unscrew the two screws that go through the part i just mentioned. they hold black rubber bumpers on the hd which hold the hd in place. (the hd is not actually screwed to the laptop, it is held in place by these bumpers. )
pop the hd cable off the motherboard, remove that cable from the old hard drive. put on new one.
pull the hd out. unscrew the other two screws on the other side of the hd once it is removed. save the little "waxed paper" sheet for the new hd.
reverse the steps for the new hd.
install the old hd in an external firewire enclosure and use for backup purposes.