The above advice is good.
If your friend isn't comfortable they can take it to a local shop. They should be able to do this for under a hundred bucks. If the Dell is still underwarranty, if there is any kind of WARRANTY problem (unrelated to the milk) Dell will refuse the repair regardless (which violates their own warranty).
The other thing is that by cleaning the keyboard you won't get those annoying sticky keys that make typing something annoying.