I'm looking at giving my wife my MBA and I'd like to wipe it out so its "fresh" like a new one would be. I understand I can get to OS Utilities with reboot cmd-r I and do a "reinstall Mac OS X". Do I need to erase the disk first? Right now I have mavericks installed. Will the fresh install have the Mavericks or will it revert back to the OS it came with? I don't remember what that even was. Any other tips? Thanks all.