Same exact thing happened to me last spring, except mine was the fill valve and I soaked the bathroom floor so bad it dripped into the laundry room below. The plastic arm on those cheap kits is so flimsy, one wrong bend and it's done. For the ceiling, point a box fan right at the wet spot and run a dehumidifier if you have one, that saved me from a permanent stain. If the spot is still soft and squishy after a day or two though, you might have to cut a small hole to let it dry out or you'll get mold up there. Also check the water line going into the tank, that's what actually got me the second time.