2 - 4 horas
I wanted to add a SSD as my primary hard drive and use the one that came with the Mac as a secondary drive. I didn't want to pay Apple over $600 to get there.
The repair went very well. The Mac Mini 2011 Dual Hard Drive Kit from iFixit is very well thought through. It has exactly what you need. The online instructions (page by page and video) are great. Everything worked perfectly.
It would be nice if the instructions explained how to put the computer back together again after adding the hard drive. It wasn't always an exact reverse of the steps to take it apart. For example, it wasn't clear how to re-connect some of the connectors to the logic board and took me a few minutes to figure it out.