I dropped my sgh-a437 into

Question

i dropped my samsung sgh-a437 into some water, and after it dried out worked fine for a month. Now all it does is vibrate when i install the battery. I'd like to get to the circuit board and check for corrosion i may be able to clean, but i can't figure out how to get inside. i removed the four screws but i can't seem to split the case. how do i get inside?