Got wet near magsafe connector, won't turn on
So my partner dropped his MacBook Air into the bathtub. Yeah, right, I know (shaking my head).
The top-left corner with the magsafe connector got wet and the laptop flashed and went black. I turned it on its side and several drops of water poured out of the USB port on the left side. After 2 days, I took it to the Apple Genius bar and they opened it and said there was still moisture inside and signs of corrosion and that it would cost $800 to fix it (replacing various boards and battery), but they didn't try to power it up. They recommended just letting it dry out for a week and praying.
So I've had the laptop open and drying for more than a week. Today, I tried to power it up from the battery and nothing happened. I then attached the power adapter and still nothing happens. There are no sounds or indications from the Mac and no lights shown on the power adapter at all. I then tried the power adapter from my old 2008 Macbook Pro and I see faint flashing amber lights on that adapter when it is connected to the laptop.
I am considering trying to replace the I/O board myself. Do you think this would be a good first step?