It sounds like you would like to turn a ranch style house into a cape style house.
If I were going to do a project like this, I would have a full dormer on the rear. Just making this into a cape will not give you the room you need.
Now with that being said, I would go to the local Building Department and ask about construction projects like what you want to do. Look at the permits and see what they claimed it cost and who did the work. (phone numbers should be there as well for the owners and the contractors)
It is against the code of ethics to give referals but, all the information is there for you to see.