FYI...I did this fix, upgraded my mid 2011 27" to a Samsung 850 EVO SSD Hard Drive. Everything went great except for two parts...
1. When I started up with my install media I got a three beep error and I could not install. I ended up using the CRTL-R at startup and did a network install that downloads an image of the original OS that comes with the system and allows you to install with the correct file.
2. Hard drive fan was spinning at full speed the whole time. This was annoying to say the least. Another person on this thread commented on this and said that you had to buy a $30 piece of software to fix it, I actually found another one that is free and works quite well (http://exirion.net/ssdfanctrl/).