My battery was at times barely lasting for half the day. It would randomly shut down even while displaying a reasonable amount of power remaining. Processor slowdown is real and painful.
Removing the adhesive on the battery was the most difficult part. The tabs ripped as soon as I tugged on them, so I had to use the hairdryer for about 20 minutes to loosen them up enough to pry the battery up. From there I was able to grab the ends with tweezers and pull them straight out.
The screws are barely visible to the human eye. Put them somewhere where they can't roll around while you're working.