Gently bend the Jimmy outwards to pry the crack open a little larger and lift the lower housing up a small amount.
There are several plastic clips on the lower housing that fit into a channel in the aluminum top housing. Your goal is to use the Jimmy to push these clips inward enough to free them from the channel, while gently pulling up on the lower housing.
Later in this guide you will remove several recessed Phillips screws. Bit drivers are generally too large to fit in the recesses, so be sure to have a thin shafted Phillips screwdriver on hand.
First remove the AirPort antenna (the larger of the two), located near the power button.
Slightly squeeze the two retaining arms toward each other and lift the AirPort antenna off its post.
Squeezing the two posts excessively will surely break them off the internal frame. Work delicately.
During reinstallation, you will have to slightly squeeze the two posts together so they fit into the openings on the AirPort antenna board.
Lift the audio board ribbon cable up out of its socket.
If it refuses to lift from its socket, the ZIF cable lock is not fully released. Make sure it is evenly lifted about 1 mm from the socket on the interconnect board.
In the next few steps, you will remove the four Phillips screws securing the internal frame to the bottom case. Included in each step is an overview picture showing the general location and a closeup showing the actual screw.
Remove the recessed Phillips screw near the power button securing the internal frame to the bottom housing.
Push the PRAM battery toward the center of the logic board and pull it up out of its holder. You'll have to push the battery in further than you'd expect in order to get it to pop free.
Don't bend the metal finger too much or it will break off, requiring a new logic board.
When inserting the new battery, make sure the side with writing along the edges faces the black plastic holder. You should also insure that the metal connectors make contact with the battery (you can bend them forward if they do not).
I used this guide, to replace the two 256mb ram cards with the max. two 1gb cards, because of the great photos...much better than a video. But if I didn't have to upgrade the memory, all I would've done is remove the airport antenna, the frame screws and the thermal sensor cable and lift the drive up enough to clear the battery. And I did replace the CR2032 battery while I was at it.