Think you might mean the Nut. Unless the existing one is the same dimensions (height and width) it may not be worth your while swapping them. However a couple of points:
Most nuts are plastic and very cheap to buy. If you do have a bone one and it is the same width as for your new neck it is possible to remove it, just gently tap it out sideways. Levering it off will probably damage either the nut or the wood on the neck. It may not be the same height or have the string slots at the same depth as your existing one, there are plenty of YT videos showing you how to address this- take any height off the nut by sanding it onto a sheet of abrasive paper so the base stays flat. Nut slots can be re-cut deeper with old strings, nut slots can be made shallower with superglue and baking powder and then re-cut. Only lightly ( a drop of superglue) re-glue your nut in place just to stop it moving sideways as string pressure will locate it anyway
If you go to the Repairs and Technical Lounge you'll also find more info!
A final point, it is not so very difficult to make your own bone nut, just buy one of those dog bones, cut a piece off and get filing!