Don't see how opening would void the warranty.. There is no evidence seal. How would they really know and would it matter.
The USB port worries Me more for getting liquid into the mod. As well as leaking in around the switch, since its so close to the atty
I know you're as anxious as I am to find out what's wrong. I don't have a star driver to fit and have been usin a small flat screwdriver. Just don't want to risk damage to a screw head yet. I really think the most likely problem is liquid leaking past the center pin. Just got back from Walmart and it's completely dead. Charger does nothing