I upgraded my 2012 15" cMBP from a Samsung 830 512GB SSD to the newer Samsung Electronics 840 EVO-Series 500GB this morning. It's the same MacBook Pro I wrote about back in February 2013.
It was super easy to do. Just remove the bottom lid screws, take the lid out, remove one bracket, pull the SSD out and unplug it. Then plug in the new SSD and reverse the process.
I took the 830 and put it into a USB 3 external enclosure and booted the MBP from that, though the MBP is only USB 2. Then I used Carbon Copy Cloner to move everything from the 830 to the EVO. It took a little less than 30 minutes to move about 111GB.
Then I rebooted into the EVO, changed the Startup Disk settings and I was all done.
I did a Blackmagic Disk Speed test on the 830 just before I started and then again on the EVO after I was all done. There wasn't a huge difference in speed, as I expected, but the EVO did peg the needles on the test.
I also, just for fun, did a speed test on the 830 while it was connected via USB 3. That made a huge difference - much slower.
I didn't really need to upgrade the SSD in the MacBook Pro because the difference in speed is for all practical purposes, negligible. I don't believe I will see any real difference in performance day to day, but I just felt like putting in the newer version SSD.
Download the pdf version with pictures here.