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.
If your mini does not have Airport installed, then skip this step.
Grasp the Airport antenna board and lift it off of the two plastic posts holding it in place. You may need to push back the black plastic tab jutting through the lower left corner of the board.
If your mini has neither an Airport card nor a Bluetooth board, you can simply lift the optical drive up and away. Otherwise, you need to disconnect the Airport and/or Bluetooth antenna cables first.
With your free hand, pull the Bluetooth cable up from Bluetooth board and unplug the Airport antenna cable from the right of the Airport card. Caution: both of these connections are very small. When re-assembling unit after repair, you may want to remove the two screws holding the airport card to the assembly and lift the card up and out to re-attach the cables.
Push the PRAM battery in and pull it up. You'll have to push the battery in further than you'd expect in order to get it to pop free.
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).
The cables you're about to remove are very fragile - do not pull directly on the wires. Instead, try to pry up the connector directly, using your fingernails or a small flathead screwdriver if necessary.
Disconnect the power button and sleep light cables from the logic board.
Use one hand to slide a spudger underneath the logic board and the other to pull back on the black sleep light unit. Lift up the with the spudger to free the logic board from the lower case and use both hands to slide the logic board toward you.
You are supposed to replace the heat transfer pad on the bottom case when you remove the logic board. If this pad doesn’t make good contact with the GPU, you’ll get overheating and the unit will goto sleep after a short time.
My Mac Mini G4 is missing the screws for the HDD/DVD carrier and the one screw for the logic board. Can you tell me where I can buy these or give me specs so I can find replacements on eBay?