These panels have through holes for wiring. The panels are normally 4' wide and most have some type of mechanical cam-lok to hold them together. Your roof system will need to be insulated also and can be done with vinyl covered insulating blankets. The insulation is normally covered with an interior finish of some sort although I have seen it with the vinyl exposed, it is white. I am sure that your electrical system may have to be upgraded to conform to code for living space.
Barns make fantastic living quarters.
Also, a word to the wise, if you tell the building regulation dept. An explosion proof system can cost 10 to 20 thousand dollars without much effort. I have lived around and handled livestock most of my life and if my mind is working correctly you must have a barn that measures about 100' x 40' with main floor level to the peak of the roof at about 30'. I am considering turning our attic into active living space. Will 2x8s be sufficient nailed to the existing 2x6 joists or should I go to 2x10.