If you are going to solder in a new battery, you will have to carefully cut the protective tape with an Xacto blade. It's sticky, so you can just fold it around the PRAM card after you install the new battery.
Watch this step carefully! The release mechanism pushes back slightly, parallel with the surface of the logic board. You may want to gently use a sparger rather than your thumbs if you have big fingers. This is a very delicate connector. Work one side slightly then the other. The good news is that it does not offer any resistance.
I've opened the G4 four times. The official Apple way outlined above is vastly superior to the paper clip method. When you lower the screen side of the deck, a little bit of pressure toward you will easily release the clips. Definitely begin with the back (screen side) of the deck where you just remove the two T-6 screws.
I don't know if this matters, but if you are doing the 6 GB upgrade on the A2210, I put the 2 GB chip in the left slot and the 4 GB chip in the right slot (with the computer on its back and the monitor facing up and the memory compartment facing you).