My old 2009 iMac crashed and after a visit to apple could not fix my "obsolete" computer it looked like the hard drive died. Having photos and stuff on it I used the iFixit guide to remove the hard drive. When I used an external USB connector the hard drive started working and worked when I replace it. Best solution was to buy a new replacement hard drive to replace. Although I had to buy a new computer I now have a perfectly working repaired one as well.
Followed he instructions. Easy.
Found the process easy, although best to have the T8 longer as then access is easier.