I had to replace the HD as it failed after less than two years. It was a good opportunity to increase the RAM from 8 to 16 GB. So I ordered the RAM chips from Kingston and a 256 GB SSD from Angelbird.

The repair went smoothly: to anyone trying this, please carefully follow the iFixit step-by-step guide. I recommend reading at least twice the whole procedure *before* beginning. Check all the photos. During the operation itself, I had the guide open before my eyes on my iPad and followed it step by step. The opening tool is a bit fragile, the wheel got damaged after the operation, but I guess it was designed to be used only once. After all, the adhesive strips can also be used only once!

For those replacing the hard-disk with an SSD: I highly recommend the Angelbird model "SSD wrk for Mac" (http://www.angelbird.com/en/prod/ssd-wrk...), for several dollars more you spare yourself the need to use additional software to enable TRIM or persuade the fans of your Mac that the HD's temperature is Ok.