replace load bearing wall with beam

We just bought an old two story house (1959). There is a load bearing wall inside of the room on the first floor. On top of this room are second floor bedrooms, bathroom and a porch. The headers of this load bearing wall (the orange part in the attachment house3.jpg) are damaged by termite. The wall carries the weight of the second floor, a wall and siding on second floor and ceiling of the second floor (attic floor).
We are trying to replace the wall with new header beam. I have talked to different contractors and got somehow inconsistent answers. I would appreciate any help and input here.
The current header beam consists of two 2x10 and there are double 2x4 top plates on top the header beam. One segment of the current header has span of 10' and the rest header span are 3' to 5' with post of two or three 2x4s. We would like to have as few posts in the room.
The questions are:
1) If we use double Georgia-Pacific 1 3/4"x9 1/2" LVL as header, what's the biggest span we can have? Is two of these LVL enough? One contractor suggests we put three LVL side by side.
2) Do we still need top plates when the new header is one long piece? Do we need bolt and glue the LVL together? How much stronger is one 3 1/2" thick beam vs two 1 3/4" together?
3) What type of post should we use? We have been suggested to use 4x4, 6x6 and we are thinking to use 3" steel column.
4) Any special treatment of the ground needed for the post? Right now the wall is on the edge of the house foundation. Contractors say they would just put the post directly on the concrete. But I found out the ground is only a layer of 1/2" thick concrete on top of (unfilled) cinder block. I am thinking either put a large steel plate on the ground and then put the post on top to distribute the weight, or dig a few small holes and try to fill the cinder block with liquid cement. I would like to avoid digging big 3'x3' post hole in the middle of room, also there might be a sew pipe under.
Thanks

The top plates are not important and can be changed out when you install the beam.
We also call those cut studs cripples but you may as well know they are jack studs.
You will get a mixed bag of suggestions here just like your contractors. An engineer is the guy that should decide the size of the beam, the length that the foundation will support on posts, dictating distance between posts and how big they should be. Once you have that plan in place now you can get quotes from your contractors, all quoting the same job.

You would do best by consulting with the manufacturer of the load-bearing products you intend to use. Both Georgia-Pacific and TrusJoist (Weyerhaeuser) have engineering staff to assist in determining what size and type of products would work best for your situation. Or hire a local engineer to crunch some numbers for you after doing a site visit, and possibly come up with a design for a built-up beam that you could fabricate on site. Going that route would be a lot less expensive for the materials (when I last checked for prices on TrusJoist Parallams for a remodel, a 30-foot, 5-1/4" x 14" was going for $795, and that was 11 years ago). Your local engineer could also make some column and column support recommendations to best serve your needs.

Anything can be done...it's all just a matter of cost. An engineer will be able to tell you what's possible...you need to do the research into costs with contractors. As Neal said, use the engineer to get the facts...not a contractor that will frame it up and say "That ought to hold it"

Also figure if you want a flush or boxed-down beam...changes the labor ALOT.