I would re-check what your contractor buddies said. If you have a second floor over this area, you would need way more than a 3" square tube steel beam. Even if you have a one-story home, the roof load alone would probably still call for a 6" high by 3" wide steel I-beam, or triple 2x8ís. Maybe you just misunderstood your friends.
If you have a second floor, a possible choice would be a 9.5" x 3.5" x 12í laminated wood beam, let in so that the second-floor joists would hang on each side, level to the laminated beam. In that way, your ceiling would be smooth, with no part of the beam showing below the ceiling height.
A word of caution, though. This is defiantly a permit-required project. Your municipality may also require a structural proposal from a structural engineer. I worked on a similar project, and even though I am an engineer and could calculate the loads myself, my township required me to obtain a proposal from state-licensed structural engineer. So a book may not be enough.
Please donít try to go around this. If the house falls down, your insurance will not pay if the proper permits were not issued, and signed off on.