Old battery no longer held a charge
99% of the time spent fighting the glue on the old battery. An iFixit Opening Tool and a old credit card worked for removing the case and old battery. the Spudger helped with removing ribbon cables.
1) The correct screw size for my nexus 5 was PH000
2) For the new battery attach the ribbon cable BEFORE placing the battery in the slot
3) An old credit card or loyalty card can be really helpful in case and battery removal