Does ANYONE know if you have to put the same size chip in your PB to upgrade the ram as the original? Can you have a 512 DDR2 chip and a 1GB DDR2 chip? If they must be the same, will Apple install your own ram for you (internal slot)? I want to upgrade the internal ram to 1GB but dont' want to pay for the apple ram (I want it from newegg)...will they put it in for me?