I am an electrical engineer. I had to take a few structural classes for my degree. That being said, I don't think hiring a structural engineer would be my first choice on solving the problem. They would be guessing at the loading anyway. Depending on the span and what is above it, I would look for a competent framer or two or three and let them bid the job. During the site visit I would ask them what size beam they think is required. The spacing and number of ceiling joists and roof rafters resting on the top plate is always a good indicator of the load. That's my two cents.
