We have a new tile floor and bathtub tile. The drains are now slow and probably need replaced (cast iron). Should we go through the ceiling from below (very nice flawless plaster) and through a side wall to replace and tie in or tear up the tile floor. We didn't want to get rid of the old cast iron tub. Can plaster ceiling be repaired to look like it is today (flawless) with a drywall patch?