If you put all the centers weight on posts jacking probably will crack
the floor then sink again. If it was built right it would not have sunk
in the first place. Forget steel replacement if beam is not rotted.
Unless you want the space and are willing to pay, But if it is low it
still has to be raised over time. An amateur could also have a disaster
for you as load on both sides must be transfered off the beam and not
shift. Jacking is easy beam replacement is not.