newel post

Hello all. A fresh newel post is desperately needed here. It seems to me that removing this old thing is out of the question. Am I right in thinking a new post should be cut nearly into the stairs and butted up to this existing one? I am worried the handrail wouldn't line up with the stringer...

We want to add a cupboard under the stairs and upon creating a hole where we want the door we found a large cross beam in the way that is attached to the newel post. We have a dog leg stairs with a turn landing. Is this beam just belts and braces and can I remove it without affecting the newel...