Ugs From what I know, a factory reset will not reinstall missing or corrupted system files or revert the OS to its original version. It wont bring back the packages i accidentally deleted.
It depends on what you did and how.
If the system boots without a red "corrupt" warning, the system partition should be intact and a factory reset should work.
If you are planning to reflash anyway, why not enable OEM unlock, boot into Recovery, and try a factory reset?