Dash board doesn't need to come out.
They'll just break the screen from inside so that all the glass pieces will fall outside.then they'll detach the rubber molding which encircles the screen and remove the silicon which binds the screen to body.then attach the rubber to new screen.put silicon on the body and put back the screen,and that's it.
u'll have to drive carefully for a day or so,then just check for any leaks by throwing water on screen.Normally agar kisi insan kaye bachaye naye lagai ho screen tou leakage nahi hoti.otherwise u'll have to put silicon in the leaked place.