that's understandable on asus' part.
liability avoidance?
what maybe going on in the ASUS support guy's head: (if you're going to mod it, do it at your own risk. i work for asus and i'll get into trouble for teaching you how).
and because the above is likely true, any advice you get in here (should it prove possible) would have its disclaimer attached. anything you do to that laptop, even through the advice of others, is solely your own to blame if it borks.
with the above said, if i don't deliver something... i kind of feel like a bad guy.
😕so, here's an idea: google or youtube search your laptop model teardown.
did it for you, found two videos on youtube:
https://www.youtube.com/results?search_query=G501VW+teardownexact string didn't return anything. i'm thinking, if i were you, i'd improvise the search strings and look for the ones similar enough, then compare it with my own laptop guts' layout.
(it was at this point... i'm tempted to ask and go look through the entire video to see the M.2 dimensions)
quick tip: these numbers... 2240, 2280, correspond to the m.2 drive dimensions. 2240 = 22 mm wide, 40 mm long. 2280 = 22mm wide... 80mm long. get it?
if the dimensions (sizes) fit, i don't see a reason why you can't just take the old one out, and slot the new one in.
think of it like playing LEGO for adults. switch stuff around, power it on, see if it works, repeat.
disclaimer: don't come looking for me if your laptop blows (unlikely, but please don't look for me. there's a reason even asus support dude won't want to tell you how)
no siggy, saw stuff that made me sad.