i AM REPAIRING A HOLE IN A CONCRETE BLOCK WALL WHERE THE PREVIOUS OWNER HAD PLACED AN AIRCONDITIONER THROUGH THE WALL. IS THERE ANY THING SPECIAL I NEED TO KNOW, DO OR BE CAREFUL OF. I HAVE THE EXACT BLOCK THAT MATCHES THE REST OF THE WALL WHICH I FOUND ON THE PORPERTY THE HOLE IS ABOUT 2 FOOT SQUARE AND 4 FEET OFF THE GROUND........HELP!!!