dont think it will be timing chain i'm pretty sure 300 i6 is a gear on gear mesh no chain. Could be cracked head, block or headgasket. I would start by doing a compression test.
as for question 2 it all depends how much damage was done. You might be better off buying a used working motor and rebuilding it.
as for question 2 it all depends how much damage was done. You might be better off buying a used working motor and rebuilding it.