Apple is coming out to my house to replace my hard drive later this week. I qualify for a free new one since my Seagate one was recalled. My question is this: I'm currently backing up my HD right now on time machine. Once they install my new hard drive do I reinstall the OS X that it came with on the dvd and then go to time machine to select 10/22/2012? or do I have to reinstall OS X 10.7 as well and then go to time machine to choose 10/22/2012?