I agree, sounds like the DC-in sound board. But do you know which side of the machine the water spilled on? If it's on the left, and on the DC-in/sound board itself, that increases the chances that replacing it will fix the machine, and if it's on the right, the chances that it's the logic board itself increase. Often you can spot physical evidence of the liquid damage on the components, and that will give you hints, so taking the machine apart might be worthwhile. Also, if there is visible corrosion/residue inside which can be cleaned up with q-tips dipped in rubbing alcohol, that act in of itself sometimes brings the machine back to life, so I'd give that a shot as well before ordering parts.
There's always a risk in replacing the DC-in/sound board that you'll find out it's actually the logic board, but you have a nice enough machine that it's worth the risk.