I bought a Refurb macbook pro, and I assumed it would come like new. I can see faded spot where the keys were greasy from the previous user. Apple put something on it to make the spots fade, but in the light I can still see the spots. Is this something that generally happens, or not? Also, what can I do to make sure everything is in perfect working order, like is there a checklist of things I should check out? Thanks