Yikes. Water damage is very serious, and is generally uninsurable and non-repairable. Sorry to hear about it.
All it takes is a single micro-bridge of salty residue from the dried water across the very small clearance of conductors on the circuit board to cause such a problem.
Of course you risk making it worse by trying to repair.
Your post does not say whether only the keyboard got wet, or if there is a chance the spill was worse than that.
If the SP4 was mine, I would try carefully placing the device into a very dry environment, such as in the refrigerator, for about 30 minutes, then removing it and allowing it to sit at air conditioned room temperature for 30 minutes. Repeat this 3 or 4 times without powering on. The idea is to keep humidity low while changing temperature, which may allow some residue to dissolve or disperse due to very slight condensation. Do not use the freezer -this would be too extreme a temperature change.
You risk making the problem worse with this remedy.