Since I just bought a new rMBP, I'm giving my old 2007 MBP to a family member. However, the battery has needed serviced for awhile now. I'm looking into buying a new one. Is THIS the correct battery I need? It looks the same, but I just want to be sure. It is the pre-unibody model of course. Also, is there a cheaper place I can purchase a battery? Thanks for any help!