The cooling fan in my early 2013 rMBP makes an annoying rowl/clicking sound when running at a low speed. It's like a low-pitched version of the sound a standard laptop hard drive makes. It's not loud, but it's definitely audible in a quiet room. Is it possible to replace these fans in my macbook myself without much trouble? I figure while I am in there, I could put in new thermal paste too. I have some TX-4 I'd like to try out anyway.