A leach field with a distribution box will allow a larger flow rate compared with a single back and forth pipe with no d-box. Peformance of a single back and forth pipe is further impaired if the field is sloped overall from one end to the other because there are uphills in the pipe path. This could pose a problem when large flows occur such as from using several plumbing fixtures and/or the washing machine at the same time.
Tornado victims: Do not rush to rebuild. Take your time and look for and get a good contractor. Or consider selling the property and moving to a home that is ready to live in.