Do yourself a favour and remove every core plug from the block beforehand. Both ends of the main oil gallery, back of the cam bore, all five on exhaust side of the block, water passage under the bellhousing contact area.
Also chip out as much corrosion as you can from around the insides of your water jacket. Use (lightly) a hammer and small flat screwdriver.
Otherwise you will get to find out just how dumb the rebuilders can be. Give them nowhere to hide when cleaning the block... I would also have them install the new cam bearings after your taken the block back to final clean it yourself (post-honing).
That's assuming you have compressed air and a supply of wax/grease remover. I use a new 1" paintbrush with polyester bristles, and a couple of smaller bristle brushes, plus make my own "pull-through" tools for cleaning the long galleries. Used with copious amounts of solvent and then blown dry immediately with compressed air, it gets things acceptably clean. Protect the bores with motor oil (not WD-40) wiped on with your hand. This reduces lint contamination. It will also test if you removed all the sharp edges!
Besides "breaking" sharp edges, check for gouges in gasket surfaces and wipe with a smooth file to remove them. Chase/clean all threads (with a chasing tool and solvent, not a tap) to the point where you can shine a light down the hole and see shiny metal at the end.
For a novice, I'd suggest 4-6 hours of cleaning to get the block sorted. Now you can take it back for the cam bearings. A second flush and brush afterwards (nowehere near as thorough as first time) will be needed in case any fine shavings are released by the install process.
Then mask off the gasket faces to apply your engine paint. If you are not sure how much to mask (eg, for fuel pump) mask the whole area, poke a hole through to set the item against the block and trace its perimeter on the tape. Now cut the excess tape away with a utility knife.
I know all of this seems a bit thorough; maybe almost histrionic. But I've been on the receiving end of incompetence enough times to no longer trust people with oddball motors (and this includes sixes in many situations). They have no respect for what you're doing.
