Chosen Solution
Ultimately I was able to replace the HDD without any trouble. I could not identify where the stock SSD second drive was located, as nothing looked out of place. Bottom line to anyone in the same boat: Nothing was different enough that the iFixit directions couldn’t be performed just as written.
I do not see an option for this set up on the 2011 machine, would you give is the serial number located on the bottom of the stand. You may have to open it up and look at what set up it has and I would appreciate it if you posted a photo. As to replacing the main drive, Apple used a proprietary heat sensor on this and changing the drive will cause run away fans if not address. OWC make an adapter that fixes the problem https://eshop.macsales.com/item/OWC/DIDI… Here is an extensive list of both the 2.5" & 3.5" drives available. https://eshop.macsales.com/upgrades/imac…
