Replace the seat, carpet and repair the floor panel.
However, if the bullet went through the floor panel thats a whole different story. A through inspection would be required, becuse depending where in the aircraft the marshall was, you could have considerable damage, that will take a lot of time to fix. Under the floor there are wires, cables, cargo compartments, fuel tanks, air conditioning ducts and black boxes of all types and functions. Not to mention damage to internal structure and a possable hole in the fuselage.