Where is it leaking? It may be a relatively simple upper timing cover seal leak (common).

With the head off, the head deck surface of the block is prepped by scraping. It's an art. When I do it, I line up a bunch of tools with varying degrees of sharpness. Sometimes the duller tool do a better job of lifting off the residue without gouging the surface. Sometimes you need the sharper tools to carefully shave off the residue. I finish the surface with Scothbrite dipped in oil. I don't fuss much with the debris. I put rags in the cylinders. The coolant should probably be flushed and oil changed after the job.