Almost time for the machinist!

Clean it/leave it, doesn't matter in the over all scheme of things.........if the shops method of cleaning is to bake and shot blast, the block will look like a brand new piece of iron, chemical dip will lift anything stuck to the block...........however, you could look upon the removal of goobers/crud/etc as one more chance to inspect the block just to make sure there are no surprises.

If you haven't already, you can take this time to knock out/remove all soft plugs/oil gallery plugs so you have an idea of what goes where when you put the new ones in.