Dismantling the Mini was simple, but the two hardest steps when installing a new hard drive were sliding the drive back in aligned correctly, and replacing the antenna grill.

Even with the logic board pushed out, I found it difficult to line up the screws on the hard drive and get it seated properly. As for the grill, it would not line up with the screw holes. I had to use the Mac Mini tool hooked into a hole in the grill as a lever to lift it up and in towards the lip of the rim it was sitting on. There was an audible snap as it settled into place.

There's no real need to disconnect the antenna. You can just lay the grill gently on its side and leave it connected.

You may not find it necessary to push out the logic board in order to slide in (or out) the hard drive. It helps to have the extra room to maneuver, but it can be done without.

That third screw on the lower right hand side should be removed in the beginning when you remove the fan.

I did not remove the IR sensor. I attempted to and it was very difficult, (I felt like I was going to snap or damage the logic board). I would advise skipping this part since it's not necessary to removal of the hard drive, and it seems like a number of people have damaged their logic board while trying to disconnect the IR sensor. Skip.

The antenna connector is underneath a black flap. I just lifted the flap slightly with a spudger and used my fingers to disconnect.

The fan has in fact, 3 screws that need to be removed before you can lift it out.