Chosen Solution
Follow this guide: iMac Intel 27" Retina 5K Display Blade SSD Replacement Be very careful on not inserting the credit cards or pizza cutter tool to far as you don’t want to damage the display. Also don’t force or pry! Follow the guide carefully. Use the custom Apple drive from BeetsTech don’t skimp with other SSD’s. If you had a MacBook Pro then its not such a big deal with the drive fails here you really don’t want to go this deep again. Once the drive is installed use some painters tape to hold the display on while you test things. Don’t stress the display cables as well. Use Disk Utility to format the SSD with GUID Journaled (HFS+) if you are still using Sierra, otherwise GUID APFS. Then run the OS installer and the end it will ask if you have another system to migrate your data you want to say yes and now point to the HDD transfer the user accounts & Apps not the data. Last step is to select the SSD as your boot drive user the control panel Startup Disk.
