How to remove the newels
If the newel has a turned profile, it may be either fixed to the newel base or an integral part of the newel base. Either way, the newel will require removal if being replaced. Note - the newel base should remain in place and not be removed since it is usually a structural part of the stairs.
It is advisable at this point to check the height of the newel base and compare it with the required base height shown in your instructions. This will depend on the system you have chosen. Mark out the newel accordingly.
Using a fine toothed handsaw, cut the newel squarely.
Note that in some instances, the newel may be fitted with a steel bolt. Take care when sawing to avoid damaging your tools.
The newel base height may not require adjusting if replacing one turned newel for another. But check anyway. If the height of the base is ok, then, using a fine toothed handsaw, cut the newel squarely and as close to the newel base as possible without damaging the base.
You may have a half newel post located on the landing against a wall. This should be carefully removed and replaced with a new half newel base cut to the required height. The new newel base will have a pre-cut hole at the top to accommodate the new half newel post.