iFixit wrote a good post “Mac Mini Late 2012 Hard Drive Replacement” with many photos. It helps me to replace the existing hard drive in Mac mini (Late 2012). I would like to contribute two more tips which would accelerate the process.
Put the Hard Drive to Mini in a Vertical direction
I didn’t follow Step 13 and after to pull the logic board. It’s okay to pull the hard drive away from the small space.
Antenna Plate Must be Insert Perfectly
Make sure antenna plate has been insert perfectly or you won’t be able to secure screws as mentioned in Step 8. It\s very small different and difficult to tell. Following photos would help you to compare.
I use a screwdriver to help on position the plate.