1 - 2 uren
The drive it came with (1TB 5400 rpm) was painfully slow; took long to start up, slow opening of apps; noticeable delay in opening Finder windows. It felt no faster than the 2009 iMac it replaced. As an interim step, I ran it with the SSD in an external usb3 case, and this was an improvement. But my intent was always to put that SSD inside the iMac.
It went well. I was very cautious about cable disconnection, having messed up a Mac mini once before by prying off the receptor from the motherboard. In this case, the pictorial guide makes it look like you just pull on the display power cable to unplug it, but when I started to do that it looked like the wires would separate from the connector. From another guide, I found that you pull from plastic tab, not the wires. The replacement adhesive strips were well-marked and easy to position.
Take your time and go through each photo before doing the step. I recommend that you use the OtherWorld Computing video along with the iFixit guide, just to make sure you detach and replace cables correctly - you can see different things in each guide.