This is more of a general guide than a strict how to.
Step one Meeting with the clients (Ok they are my parents) we established several things.
About 6 feet long so it wouldn't hit the bookshelves.
Above the fireplace higher than what they have now so some art will have to be moved.
Wood was chosen because it fit with the house but the species changed 4 times.. From Spruce to Pine Glue lam beam to Cherry. Finally Red Oak Stair Treads were Selected and used..
This was a bit of a issue.. The Client wanted unfinished, but wood needs to be sealed to keep it from blowing is self apart during seasonal changes, so I used Semi Gloss Spray.. This should keep the peace.. But Finish can be used to hide all kinds of flaws. If a client doesn't want the wood finished to save money or time my advice fight them on it..
I would suggest is not discussing price until you have made a proof... it will give you a better idea of how much time and effort a large project will take. Never apologize for your price.. If they can't afford it you can't afford to make it..