MB took a drink. Still Powers-up and appears to charge. No Display

So my 9 year old daughter spilled water on our MacBook 13" Unibody (Model A1278) Late 2008. I wasn't too worried because she said the lid was closed. But, upon further interrogation, I learned that she opened the lid and water got onto the keyboard area she wiped it off with a paper towel and quickly closed it in an attempt to hide it from us. That is, until her 4 year old brother ratted her out...

The MB would have been asleep prior to her opening the lid - not powered off. Meaning, there must have been a short period of time where the laptop was powered on with water dripping down though the keyboard onto the logic board.

I opened the MB and held down the power button to manually power it down. I then put the MB into a large container with rice and left it there for over a week.

I then plugged it into the charger and the light went from orange to green over a period one would expect the MB needs to take a charge. I then tried to power it on and observed that it appears to be getting power because he back light of the keyboard comes on and i can hear the fan working but I have no display.

So I powered it back down and, now, I'm debating what my next step should be:

1. Hook it up to an external monitor to see if it works - wondering if I risk causing further damage to the logic board.

2. Just clean the logic board to remove any corrosion as a first step - if so, I'd need detailed instructions on how to clean water damage.

NOTE: I'm attaching the highest res picture my iPhone allows of the MB with the lower case removed. I think I may have spotted some corrosion in case anyone with sharp eyes is able to confirm. Although, I suppose if i have corrosion on this side of the logic board, it's likely for corrosion will be on the other side as well. I guess I'll need to remove it and clean both sides so am really looking for some best practices in this regard.