I completed this today and it was easier than I had imagined. I have replaced the drives in around 30 of the older iMacs and I was a little annoyed about the screen removal process for this one (which is my daughter’s one)! I couldn’t find a use for the service wedge…
The hardest thing was getting the SATA cable back in, I ended up removing the rubber casing from the new drive and then plugging it in, there was more room and with the help of a spludger it was easy - I then eased the cover back on. I used an intel 545S series 512GB SSD.
My advice when following this guide is to take your time with the iMac opening tool and cards (and mark 3/8 inch on the card with pen) and if you can find an extra pair of hands then that’s good too. I had some help so we didn’t need to completely remove the screen, it just tilted back quite nicely. I didn’t need to worry about replacing the adhesive strips in the hinge area either.
The screen data and power cables were easy to manage.
I have replaced the hdd in this model about 8-10 times - I have never had to disconnect any cables other than the sata and temp sensor cables on the hdd. I just prop the lcd up with an egg carton (or something about 3 inches high that is soft and light) and access the hdd that way. The only thing I ever have trouble with are is putting the LCD screws back in around the magnets - but I have pretty much perfected that with a sissor/ tweezer tool.