You have a few options depending upon its age and general condition.
1. Replace the differential
2. Sell it as-is
3. Part it out.
4. Weld a patch over the hole (if the differential casing is weldable).
We can't really decide for you. We can only give you options. Probably #2 or #3 because of it being 11 years old unless you can get a free or very low priced differential.