How does a wet DS get fixed?

My son wet his DS while at Grandma's (he said it needed a bath). So I called the DS techs at Nintendo, they said to take the battery out and leave it out to dry by a window. So I did, it worked, but now after two days it stopped working again. I don't know if I should dry it out again. Also, I got a repair quote for $75.00. Has anyone ever sent their DS to get fixed for water damage? If so, what were the results?