Bei Schritt 9.2 (Kunststoffkappe vor NFC-Antenne hilft es, die Kreuzschraube links neben dem NFC-Anschluss zu lösen, dann lässt sich die Abdeckung einfacher entfernen. Ansonsten funktioniert die Anleitung sehr gut.

Worked almost fine for me! Found replacement battery on ebay with original model number.

The only point I somehow struggled with is the fact that there is no option to shut down the paperwhite. The only options my device provide are reboot and display off (and cancel of course). However, I selected reboot, lowered 2 screws from the battery and before booting up again I removed the last screw and replaced the battery.