I want to remove a load-bearing wall to join two rooms together.  The structure is a single story (circa 1950) post-pier home with a low, gabled roof.  Because the roof is low, there are soffits on the east and west ends of the home to conceal the roofline.  The soffits run north-south and the wall to be removed rubs east-west.  

To handle the load, I want to remove the 4x8 beam that runs along each soffit face (because of this bean, the soffit is rectangular rather than sloped) and replace it with a steel beam.  Each end of the beam will have a steel post going into a cement footing under the house. The span of each beam is 27'.

1) I need to know the minimum sizes of the beams and posts I need.  The smaller the beam, the more "shallow" I can make the new soffits.

2) Do I need to weld the beams to the posts? Can I bolt it?

3) What book(s) do you recommend I reference for this problem?

4) Is it necessary to envelope the steel beams (and posts?) in wood?  Is this for fire safety?

I appreciate any info on this...