Re: Is there hope for an engine after an overheat?
What do you mean when you say it "suffered an overheat"? Did it get warm for a minute or (as it sounds) get real hot for a while?
Probably not a bad idea to do some more digging. You can pressure test the block with the heads off, but would need air and plates to block off the water passages except the one you're putting air to. The only way to know for sure is to take stuff apart and look at it. If everything looks in order you're looking at a hone, rings, and bearings, which a competent machine shop can handle without issue. Plus replacing the heads.
Or you could keep your fingers crossed, just replace the heads, and see what happens.
A long block may seem like overkill, but if you aren't doing the work yourself you have to figure that the money you pay the marina to check stuff out is money that could have gone towards a long block. And hourly rates for that sorta thing can add up quick. Keep an eye out for Murphy.