We all know Apple charges stupid amounts to upgrade from 2GB to 4GB. Because of such the consensus usually is to buy the memory elsewhere and install it yourself or have someone certified by Apple to install it. That's where my question lies. Is Apple's warranty null and void if a user replaces memory in his/her MacBook? Also, how much would Apple charge, if anything, if I took it in to ask them to replace the memory? Thanks for any information.