Depending on the size and exact location of the hole it may very well be fixable. Many people have fixed holes or breaks in their cases using products such as j.b. weld, epoxy weld etc. I have personally used epoxy weld made by loctite that is made for use on iron, steel, aluminum, brass, bronze, copper and pewter to repair my case with great success ! It can withstand upto 3355 psi and temps upto 300 degrees F which makes it ideal for use on motors and/or cases. Some pics would help to assess the damage so we can determine the seriousness, therefore determining if its an easy fix or if you should have a professional do the work.