Macbook air got wet, wouldn't operate under A/C power, USB damaged
After purchasing some pentalobe screwdrivers and small torx bits, this repair was fairly easy to do, being mindful of the different screws and their placement. The logic board, wifi card, and IO board got wet while in my wife's carry-on bag with our child's leaking sippy cup. We submerged the entire laptop in a few pounds of dry rice as soon as possible and left it for a week to absorb moisture, then opened the laptop up. I used a small nylon brush (a toothbrush would work well) to wipe off all traces of corrosion from the solder traces and components on the logic board (I took it out completely using the appropriate tutorial here). After this point the computer would boot up and operate under battery power, but the USB port on the logic board wouldn't work, and AC power was inconsistent.
I took the computer back apart and decided to replace the IO board and cable, because I could see corrosion in the very small and impossible to clean connectors for this cable. The new IO board came the very next day (coming from California to Canada!) and went in very easily thanks to the tutorial.
I'm happy to report that the repair was successful, and much cheaper than buying either a new logic board or a brand new macbook to replace this one, which was barely a year old.
If your Macbook gets wet, I'd skip leaving the entire laptop in rice and get it opened up right away to remove as much water as possible and cut down on corrosion to your valuable components and cables. Disconnect the battery cable from the logic board straight-off to prevent any (further) electrical damage to the computer. Once it is opened up you can remove the logic and IO boards and give them a blast of an air sprayer to get most of the water off, then leave those in rice for a couple days to really dry them out before cleaning up and putting back together to test the laptop out. Make sure to verify operation with both battery and AC power before closing things back up, since IO board damange can cause either or both of those to fail to work properly. A magnifying glass was very helpful when cleaning all the corrosion off the logic board and for inspecting the condition of the various ribbon cables and connectors.