Hershey bar wing vs composite wing - how much drag?

I have a Cherokee 180, with the short hershey bar wing. While I love
the plane, I always wish it could go a bit faster, or use a bit less
fuel to get to my destination.

I have followed the composite homebuilding movement for many years,
and am amazed at the sleekness of a composite wing. The wings on most
composites tend to be the complete opposite of a Hersey bar wing:
high aspect ratio, low thickness, no rivets, no screws for fuel
tanks,smooth curves faired into airframe, and streamlined landing gear
structure.

So my question: How much drag does a wing on a Hersey Bar Cherokee
generate, and and hypothetically speaking, how much faster could the
plane go if it was retooled with a sleek, composite wing?