I did it!

Mijn probleem

Battery wear was already at 30% according to the Battery Life app, and a replacement seemed the only way to go.

Mijn oplossing

Got myself the Replacement Kit from iFixit, and used both the video and the pic tutorial do do it step by step.

Removing the adhesive strips were indeed the hardest part, as both left and right broke off early. I then used a hairdryer to melt away the strips, but it was still gruesome to remove the battery.

After installing the new one and reassembling the phone, when I turned it on half the screen was black. I panicked! But then opened it again and checked all the cables. They weren't perfectly connected! Re-did it and now it is perfect. Battery Life app seems to think so as well!

Mijn advies

Adhesive strips were a pain. And carefully check all cables, firmly pressing them down to assure they're connected.