No, N:TW is a completely separate game, albeit it quite similar to E:TW, which the creators quickly and unceremoniously abandoned supporting in favor of making the next title to profit from. I haven't played N:TW enough yet to tell you if there are any real changes, but it should be easy enough to google and look up. Shogun II is still too damn expensive, in my opinion, especially at the rate they are releasing games these days. It came out in what, March, and they have already admitted to moving on to the next title. Good thing these games have talented and committed modding communities.
Edit: and yes, Clark, their mod is safe. I haven't played it specifically, but if it's listed on the TWcenter forums, chances are it's safe. No mod will ever be 100% stable, but generally those good enough to garner their own spot on the forums there are good enough to be worth trying.