I have a second hand refurb Mac Pro. I'm trying to figure out whether to upgrade to 5.1 but I have a few questions: Does doing this mean I can't pay apple to service this mac anymore?(What happens to my serial number?) Is it illegal to do this? Is there any risk? Is the 5.1 upgrade genuine apple or is it a cracked/modified version? Also how does a 5.1 Mac Pro know if it's a 2010 version or 2012? What upgrades can I do to my system if I stay in 4.1? (I have the base model) Thanks guys!