These are great instructions. I don’t know if anyone has mentioned this, but—
After you boot up with your new non-Apple SSD, and at least up until the High Sierra OS, open terminal and type: sudo trimforce enable. This extends the life of the SSD by giving it special instructions on how to dispose its trash when a file is deleted.
You can then go to About This Mac/System Report/SATA/SATA/Express and see “Trim Support: Yes”.
I will confirm for a third time, having just done this replacement yesterday morning: Steps 6, 7, 11 NOT NEEDED.