2 - 4 horas
Upgraded my mom's new 2011 Mac mini for only $250 worth of parts which would have cost $950 if configured by apple. $700 seemed like alot of money to not go to the poor kid in China who'd be slapping in the upgrades for me, so I decided to do it myself.
Pretty smoothly, the only hitch was that the screws for the HD that went through the metal grate did not line up with the drive once it was put back together. The drive was pretty snug without them, and since it was an SSD, I deemed them optional for now. I'll see if the SATA port disconnects when it's move between locations and fix it if something comes up.
Try not to have any extra screws left at the end. Pretty simple upgrade if you've taken apart any pre-unibody macbook pros before.
Oh, and if you're swapping out the stock HD completely, and putting 2 virgin drives in - preinstall OSX 10.7 and update it to 10.7.2 before you upgrade. Had a !&&* of a time getting the OS installed since it didn't want to boot from either the OSX 10.7 install disc OR USB recovery drive since the mini wanted 10.7.2 in order to boot - kept getting the no circle/slash symbol on boot after the upgrade.