I'm going to do this now as multiple things are going wrong with my phone

1) Desktop icons randomly work
2) Alarm randomly doesn't play the alarm sound (I've been late a few days to work because of this)
3) Battery gets drained within a few hours
4) I randomly get no indication of SMS. No blue LED, no SMS alert tone and the launcher button on the top left of the screen doesn't change

I'm quite savvy with Linux and anything electronic but I'm wondering how dangerous flashing the eMMC is? Is it possible to brick the phone? If anything goes wrong at any point is it possible to run the firmware updater and get the phone back to a working state?