You know the answer for that!
You could take the laptop back to the reseller and perhaps get satisfaction but ASUS will want you to return the laptop for repair (with no assurance that the HD will be replaced).
To replace the HD you must remove your bottom of the laptop and disconnect two ribbon cables. This will give you access to the HD, NVMe drive, and memory.
I have already spent more time explaining this than time spent to swap out the HD.
Good Luck
G752VSK, G75VW-3D, G51J, G1S
Homebuilt Windows Server