This is a major structural change, and you should consult with a licensed General Contractor to advise you, based on the current construction of your home.
This is not an average DIYer project.
I would second Mike's advise to contact a reputable local GC for such a project, definitely not something you should jump into on your own without doing alot of homework first. Without seeing the place first hand can't really advise if this is even structurally possible, let alone economical feasible.
All you need is ignorance and confidence and success is assured. - Mark Twain