Graph Tech supplies more of the `ukulele factories than you care to know, in some form or another. The saddle swap is no big deal, but the nut is probably glued in.
Most will tell you the nut doesn't have an impact on sound, except on open strings. Some will tell you neither does the saddle <smirk>.
Some builders will tell you its sacriledge to use fake ivory. Personally, the Dunwoodie's are awesome people to work with, and Tusq has very good machining properties - I'm sure you did the drop test already.
Also, I don't think Kamaka uses plastic.