Once the hard disk is open, it will stop being a mystery: I cannot believe it is all like the old LP players my mother had!
I notice that there is a reading head and something that is just like our LP reading system, but, instead of having a vinyl disk, we have one that looks like our CDs.
The main issue you will have is finding the position of the screws it seems to me.
An WD5000BPVT, like mine, seems to have 8 main screws: 3 hidden on the top of it, under a cover made of foil (three circles), one that is visible and by the first 4/7 of it, one that is not visible and is a bit above the line where this is (closer to the top), to the other side, one right where you read W, and two visible ones to the bottom.
You will only find opening it easy if you know where the screws are. Once all the screws have been taken out, the metallic cover will easily come out, but, before that, you may end up doing something as ugly as what the boy does in the video:
And this is an example of good and clean work: