I've got a similar thread here with no replies...
http://forums.taleworlds.com/index.php/topic,335339.0.html
I'm assuming it's the standard NW dedicated server files found here: http://forums.taleworlds.com/index.php/topic,282473.0.html
My assumption is that in the .bat file that launches NW you would flag the N&S mod instead. That's just an assumption on my part though since the few people that seem to know how to configure a N&S server are keeping the information to themselves. Even if my assumption for how to launch it is correct, it looked like there were some different variables to configure as well as the factions being entirely different, different map names, etc. All of that would need to be in the config. The only way to figure all that out would be to tear it apart and find all that info. out from the mod files themselves and I just don't care enough at this point to do that.
Here's to hoping someone with the correct knowledge will post up a guide or reply to one of these threads.