1 - 2 horas
So I was in the lucky position of having a Crucial M4 SSD and decided it would be perfect to complement the 1TB drive in my Mac Mini (Late 2012). Didn't want to spend out on a fusion drive or add the ridiculously expensive Apple SSD so to iFixit I came!
It really was not particularly difficult or even all that time consuming. Yes, the parts are very small and you have go carefully but the instructions on iFixit are very good. Time Machine is a life saver as I simply restored my Hard Drive back and now I am in possession of full SSD accelerated goodness!
Make sure you have enough space to work in and good lighting. If you are ADDING a drive and retaining the original then you MUST put the original drive into the cradle that the instructions show putting the new drive into. This will mean that you will have to disconnect the Hard Drive cable from the original drive and use the iFixit supplied cable for your ORIGINAL drive and use the Apple supplied cable for your new drive. Also you will need to extract two pillars from the original drive and screw those into your new drive. It seems that everyone who has added an SSD has found the same problem.
Also, when you reinstall the drive into the Mini (the reverse of Step 18) then make VERY sure you seat it all the way in otherwise the Antenna plate screws (step 8) at the bottom of the Antenna plate will be very difficult to put in.