riley,

Unless your iPhone has pentalobe screws, you should be able to pop the back off by removing the two phillips screws to the left and right of the dock connector. For the pentalobes, you can try a really tiny flat blade or just grabe the pentalobe tool from iFixit.

iPhone 5-Point Pentalobe Screwdriver

As long as you do it properly, Apple will not know that you've been in your phone. Would it technically violate the warranty, yes... but the genius bar would never be strict about that unless you actually broke something.

The best place to check the liquid sensors are 1 - in the headphones jack, 2&3 - along the left side of the battery. Of course, you'd have to pop the backplate off to see those.

Personally, I wouldn't have any reservation about opening it to let it dry out. Check those liquid sensors and go from there. Good luck!

Yes you will void your warranty by opening up your phone. At this point it doesn't matter since your warranty doesn't cover water damages unless you purchased some insurance that does. You do need to disassemble your phone and deal with this. The gist of the procedures to disassemble are here. Clean your printed circuit boards with rubbing alcohol and and a brush. Then submerge and agitate (move them around) them in alcohol to ensure that the ICs (Integrated Circuits)with BGAs (Ball Grid Arrays) have been flushed of contaminates. Wipe them with paper towels, changing them often, to ensure you are not smearing residues or contaminates to other places. Use a hair dryer ( on low to no heat) or a fan to expedite the drying process. With the use of the fore mentioned continue to let them sit over night to dry. Let them sit at least 24 hours with out the aide of air flow. Reassemble and give it a try. Good luck and have a wonderful day!