Easiest thing I've ever done
My 2011 MacBook Pro battery finally died. It had expanded so much, it was pushing the trackpad out of place and I couldn't do much on the machine. Went to Apple, they found the part on ifixit, it went out of stock quickly, I asked to be notified when they had more in, they notified me in the next couple of days. It only took a few days for the battery to come in.
I took it to a local repair shop where an employee used to work for Apple. He was able to replace the battery then and there and dispose of the other one in a way that was safe.
When you find your part on the website, just be sure to buy it as soon as possible