In April, I purchased a late 2012 mini (MD387LL/A) - 2.5Ghz i5 with 500MB hard drive.
It looks like Apple now secures the drive to the tray with 3 screws. 2 on back side and one on front. This means the entire drive tray has to come out to remove the drive - it no longer just "lifts out" as in step 18. In order to remove the drive tray, you have to remove the power supply (step 22).