Generally, the battery wasn't holding a charge. It manifested itself as the phone powering itself down after the battery reached nn% charge, where nn% was initially 20%, but more recently 50-55%.
Repair went well. The only issue was the subatomic screw fell into a groove in the table and my 40-something vision couldn't pick it out. I enlisted the assistance of my 15 year-old.
Suction cup is essential for getting the cover off.
Battery was well-glued, so I leveraged the left side of the case in different spots to loosen it.