Two issues you will deal with possibly:
1) Liquids tend to short out electrical circuits - very bad if it is powered on with the liquid in contact with any electrical devices. Make sure it is completely dried out. Putting a device in a large "zip lock" bag with uncooked rice (use a small towel over the rice and under the laptop to prevent rice getting in the laptop) will "suck out" the liquids. It may need 3-5 days in the sealed bag (don't open to check it).
2) The residue from the milk as Rosco mentioned can create issues with moving parts, and even the electrical contacts. Alcohol is the best cleaner - and it evaporates quickly. Using a q-tip to clean is the best way to remove this residue.
In most cases - you have a good chance of not damaging the laptop if the liquid didn't short out components.