Early 2011 Macbook Pro 15" HDD was in need of being not terrible.
Ran out of AppleCare and just had the battery replaced for being consumed and the SuperDrive for being generally $@$*!& for it's entire lifespan. Decided now that the laptop had a new lease on life it could use a slightly faster disk.
Super smooth, would not even classify a early 2011 MBPro change as moderate. The only thing that was a little nerve-wracking was removing and re-installing the battery cables so i didn't fry any parts of my logic board but I was probably over concerned with static.
Off it went, cleared a few years of dust out of the case and in went the new SSD, ran into a few hiccups when I was booting again as I forgot that the drive hadn't been formatted for OSX but once that was done I reinstalled from my Time Machine backup and was back in business.
Don't be so worried about using some force with the spudger to get that battery pin out.
Also you will need to use disk utility to format the drive, something I forgot to do, before attempting to reinstall from any back-up. Just make sure you're in wifi or ethernet range and you're all set.
Also, use two small bowls to separate the two different screw sizes for ease of re-assembly.
500 GB SSD Hybrid 2.5" Hard Drive
Phillips #00 Screwdriver
TR6 Torx Security Screwdriver