Okay... So step one....
Don't try. First, the screen comes out
through a cut out in the case. You have to remove the screen from the case to separate the case to get inside. The screen is naturally thin glass as it's led/LCD type screen. If you don't get it off you'll rip the ribbon cable off it.
Second... The 510 IS the positive battery terminal.
Is there a way to do it? I'm sure with enough time and designing it's possible but there's no easy way to do it.