Now if someone would post detailed instructions to swap an HR24 drive. I've read a little, sounds like a bear.
No harder than any other box, just opening the case is tougher.
I use a small flat screwdriver to gently pry the case sides from the bottom, there are two latches on each side. Use something to wedge between the case top/side and the receiver bottom/side. I usually use a couple index cards folded to about 2"x2".
Once you have the 4 pins blocked off, there is a release on the bottom of the receiver, maybe two if I remember right, that you pop with the screwdriver, they are toward the front of the case. Then the top lifts directly off, no angle, straight up.
Once in, it is pretty simple, 4 screws hold the black hard drive holder, disconnect any cables around the area - power, sata, fan, etc.
I have an HR24 that is running an internal 2TB drive, it was about a half-hour job being patient and careful and figuring out the casing.
BTW the HR34 is even tougher and when I talked to someone that had opened it, along with the risk of it being a newer box (and potentially less reliable), I decided not to open an HR34.