Maple French Door

I need a door at the end of a downstairs hallway where the door would be installed, there would be a 6inch gap between the top of the door and bottom of the cieling how do i fix this? my son a former hanger said i would have to knock out the two side corners at the top and nail in a 2x4 to hang the sheat is there an easer way as this will be a new house with no modifiying available before or during.

Hopefully someone will have an idea. It appears that the home we purchased had a new storm door installed and that storm door had a protective plastic film on it to protect the new paint which should have been removed when the door was installed. Now, several years later, the plastic film has cracked and looks horrible. I can scratch it with my fingernail and remove the plastic from the paint easily, but this will take eons. I have tried a plastic scraper and it works, but still taking a long time. Any suggestions on removing this baked on plastic film without damaging the paint? Thank you, Cathy