I believe Ti uses Torx T6 screws on their graphing calculators and phillips screws in the battery compartment.
Here is a disassembly guide for getting to the battery:
Texas Instruments TI-84 Plus CE Battery Replacement
Here's what is looks like on the inside:
Do your best to dry any areas that you find wet. Be careful around the LCD display. ribbon cables are very fragile and take care not to tear them. Also, you should not have to worry about water getting into the LCD display assembly because it looks like Ti sealed a piece of plastic on top of the lcd display assembly. This should have prevented water from intruding into the layers of the LCD. Otherwise, make sure the calculator is off with the battery removed during disassembly and dry any wet areas with a paper towel or similar.
The old ti-84 series lost your saved functions / equations when power was removed for a few minutes, this may still be the case with the ce version.