If the GASKET is not torn---it should be reusable.
This is a fairly simple task.
Remove the *phillips* screws on the HINGE.
Place door on a mat or towel.
Remove the screws from around the perimeter of the door and pry/separate the inner ring.
Having an assistant helps & taking a photo or two with your cellphone camera is a plus too.
Part Link ==> Door Gasket