Not complicated at all.
Just unscrew the big flat-head screw recessed on the tip of the rear of the case.
Slide the casing back, then lift up fro. The rear and towards you.
That's it.
To remove the HD, just unplug the cables and there should be a Philips/posi screw that holds the HD to the case and just undo that and it should come out with the caddy/holder.