This is a reasonably simple repair once you get the courage to pry off the bottom cap and manage to release the tabs holding the insides in the outer case. In addition to my comments above, I found that pulling the upper part of the mechanism apart from the lower part in order to expose the second screw was best done by simply pulling them in opposite directions (like a radio antenna, as mentioned above). Just don’t pull so hard that you pull the wires apart. Prying the mechanism from the magnet using a spudger was effective in separating the two.

All in all, great guide!

I would recommend against using a metal tool to remove the cap from the case. I used a small flat head screwdriver and ended up marring both plastic parts. A spudger would have caused less (albeit cosmetic) damage. The cap contains a recessed o-ring, and this o-ring is fairly robust, i.e. I did not damage the o-ring when prying the cap off with a metal flat head screwdriver. Nonetheless, be careful not to damage the o-ring, which provides a water-tight seal at the bottom of the toothbrush.

A good technique for removing the cap from the case is to work a spudger into the gap formed in Step 1, between the outer plastic part of the cap and the o-ring, work the spudger around in order to pull the cap out to expose the o-ring, then work the spudger under the plastic part of the cap below the o-ring and work around to completely remove the plastic cap.

Following the battery replacement guide to remove the insides from the case, I found iFixit precision tweezers to be very helpful in releasing the restraining tabs.

The goal here is to produce a gap between the white case and the chromed plastic cap so that a tool can be inserted between the two parts. Once a gap is formed, move on to Step 2 to pry the cap from the case.

I absolutely severed this cable when loosening the adhesive around the volume button area. There is really no way of knowing if this cable somewhat elevated from the frame and therefore susceptible to being cut, and it happens to be right where one starts to remove the face with the guitar picks. The cable is directly in from the down volume button, so be extra careful not to put the guitar pick in too far in this area. I recommend buying a power/volume button cable just in case. Replacing this cable is also not easy, but doable. Just try to avoid doing it.

I absolutely severed this cable when loosening the adhesive around the volume button area. There is really no way of knowing if this cable somewhat elevated from the frame and therefore susceptible to being cut, and it happens to be right where one starts to remove the face with the guitar picks. The cable is directly in from the down volume button, so be extra careful not to put the guitar pick in too far in this area. I recommend buying a power/volume button cable just in case. Replacing this cable is also not easy, but doable. Just try to avoid doing it.

I also had difficulty installing a 2.5" SDD using a Sabrent 2.5" SSD & SATA hard drive to desktop 3.5" bay bracket. The cables inside the iMac are just long enough for the original 3.5" drive and not long enough to reach a 2.5" drive in this particular bracket. I had to settle with an SSD held into the bracket at an angle with two screws. Somewhat shameful, but it's not going anywhere anyway.

I had the same alignment problem, too. I ended up removing the rubber grommets from the plastic enclosure, widening the holes with a small file, then replacing the grommets. All four screws went in, but not in perfect alignment. Should be ok, though.

Why no mention of attaching the new hard drive to the Optical Drive Enclosure using the enclosed phillips screws?

Once you have securely inserted the new hard drive into the Optical Drive Enclosure and replaced the plastic positioner you should attach the drive to the enclosure using two of the provided phillips screws. Two holes on the underside of the enclosure should align with two attachment holes on the underside of the drive.