Hello, I'm not sure if I should be answering this but thought I might shed some light on what I did.
I came here to ask so technical questions out of the norm and found your subject and thought, what the heck.
I have a late 2012 iMac 27" that had 8GB of memory and a 1TB HD.
A lag in the iMac led to an authorized dealer looking at it and finding a bad 4GB memory chip.
It was pretty straight forward to replace myself and very inexpensive to upgrade.
But I was hesitant because it was 6 years old, the HD was full and thought the logic board needed to be newer.
After so simple research, I found the logic board wasn't to old and did not require changing, but still the HD issue to address.
I found a third party that offered an all-in-one HD upgrade package that well exceeded my HD needs & very affordable.
I was cautious, worried that I'd mess it up.
It was so easy and had it done in 45 min I was very happy with the results of my upgraded iMac.
Since you "Q:" was unanswered, I thought I'd throw my 2 cents in
Regards