If the main bearing shells spun (which is typical) then the block is trashed too. Dealers here charge such a high labor rate, that its cheaper to replace an entire engine, than it is pay the labor needed to repair it.
As for the 0W40 oil, no it will not fix bad machining or remove debris that was left in an engine, but it does provide an increased safety margin with literally no downsides or adverse affects (other that perhaps it cost slightly more) .There is no use case, no scenario, no environmental condition ( not a single one), where 0W20 does a better job than 0W40 at protecting the engines rotating components. The only advantage 0W20 has is it offers a slight increase in fuel economy.
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