2 - 4 horas
Having an SSD in all of my systems but my Mini it made it seem unbearably slow, so I decided to add it.
I've got two left hands so I was quite afraid to break something, everything turned out fine but some of the components where stuck quite solid. I had to apply more force then I was comfortable with to open up some things and get them back together again. However everything booted up fine and I've got a working dual harddrive!
Take your time! Just follow the video and you'll be good, even without any technical skills.