the other day i was browsing and I found an review of a WD HDD, and I found this I thought replacing the HDD would not void the system's warranty. Now I am concerned since i wanted to upgrade to SSD down the line. Do you have any apple link that specify you do can change the HDD? I'd like to have a hard copy just in case in the future I need some kind of document saying that the warranty is not void. Please thanks.