How can I fill a hole in wood so that it can be redrilled?
Wood filler alone may not fill the entire depth of the screw holes.  I would use a piece of dowel, toothpicks, golf tee, or a carved piece of wood covered in wood glue and fitted tightly into the holes.  Using the wood and glue method will give you a nice dense fill so the new screw will not split the remaining original casing.