I'm always a fan of fixing an eReader (even if you just want to pass it on down). And the Kobo Glo HD seems to a great little reader (I have it's near kin, the Touch 2.0). According to this video, it looks like removing the back from a Kobo Glo HD is pretty easy...
https://www.youtube.com/watch?v=O7FuyPwc7Iw
It looks like the hardest part of the battery change process is carefully removing the old battery because (like a lot of these) it's glued on. (You just have to "work" it, pry it bit by bit and don't yank on it.)
There's an older thread on this subject here...
https://www.mobileread.com/forums/sh...d.php?t=310023