The cool thing about violins are that they are designed to be taken apart and reassembled. I wouldn't hesitate to fix almost any violin, unless everything was broken ACROSS the grain in multiple places. There is a point of diminished returns when it comes to repairs, but cracks, shifted joinery (like glue creep), split pegheads, should be fixed. Severe cracks across the grain will often require that the piece be replaced, especially if it's the top, but not necessarily so if it's another part.

Get thee to a luthier.

Peace, Mooh.