Raise the existing beam a little, maybe 1/4".
Build a temporary support wall along side the existing beam.
Shim it at every joist that isn't resting against the wall.
Remove the old beam and the posts.
Installl the new steel beam and posts.
You still need as many posts to distribute the weight on the floor.
In order to span a further distance with steel, the steel beam will have to be nearly as wide as the current wood beam.
Anyway, pop the studs out one at a time in the temporary wall.
You may have to dig the footers out and replace them if the posts have rusted out.
Best of luck to you.
Remember that steel is very heavy, It will take a lot of strong backs to get a beam into a basement. You may have to bring it in in sections and have it welded together after you get it in place.