Mechanic said I have metal shavings in my engine and now I need to replace the engine as it is completely ruined. Is this true? Please advise.

Ye its true

Did you run the engine out of oil? Metal shavings are indications of serious damage. If the engine still runs how good does it run?

metal shavings is ussal a sign like the other guy said that you ran out of oil and kept driving the car with it dry. Either that or the oil pump failed which some times they do and oil was not circulated. my advice would be to see if there is a recall on the engine for the oil pump if that was the fact cause often they will replace anything that got damaged for free due to the issue.