Bottom hole - Providing the insert you will use will allow it, I would repair it in situ, with the sump plate off and as much precautionary grease as you can manage and then flush it clean from through the hole and up through the sump, something like an aerosol with the fine tube/pipe on it, block the end of the pipe and make a little hole on the side of the pipe in the direction you want the contents to go ( contents being something that wont harm engine oil)