As a homeowner, you should reset the opener to prevent outsiders from opening the door with a remote that's set to a Liftmaster default code. A simple procedure allows you to reset the opener for one or more remotes.
doorsill - the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway. doorstep, threshold. 1  doorway, room access, door, threshold - the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close; he stuck his head in the doorway.
Before you start, bear in mind that the car will loose it's torsional stiffness during sill replacement, and also you'll need to take steps to prevent the door gaps from closing/opening up. Leave the doors in place where possible so that you can keep an eye on the door gaps throughout the sill replacement. Setting up: The red wine level gauge I use a plastic tube full of red wine to set levels.