I just picked up a refurbished rMBP with the standard 256GB SSD. I'm thinking of upgrading the hard drive myself, which looks pretty easy to do, but I know this will void the warranty if Apple found out and I ever needed to make a warranty claim. My question is: Does Apple actually have any way to tell if I've opened the computer up? Assuming I didn't strip any screws and put back the stock SSD before bringing it in, how could they tell? Not that I plan on using the warranty -- I just want to know for sure if it'll be something I have to give up if I want to upgrade. And I know, this is something I would have had done by Apple when I got it, but the refurbished selection and pricing options didn't make that a viable option when I bought it.