Original battery no longer holding a charge, occassionally suddenly dropping from 50-60% battery life, to below 10% , or even shutting down due to low battery.
Worst part was getting the glue to release the old battery.
Just a reminder if you run into the same thing... GO EASY and apply light-to-medium pressure and hold it steadily, AND remember to NOT pry against the board, but ONLY against the outer edge/case. ;)
After that, pop the old one out, drop the new one in, ensure that the grounding strap (the tiny loose piece held in place with the upper screw), is in position, snap the connector together, and insert the screws and replace the back cover...
The replacement battery came with approx 50% charge, which lasted approx 30 hours, before it got down to the recommended below 10% charge level before shutting down and performing an uninterrupted FULL charge, to help set battery memory for a longer life. That took approx 3 hours, and the replacement battery has approx 80)+) hour life now... SWEET !!!! ;)