Wii U: Nintendo Network ID and cleaning tips?

I just bought a used Wii U. The guy i bought it from don't have any digital games on it (he didn't buy any). Can i just delete his Nintendo Network ID and link my own that i use on my 3DS? I've also heard that the console and gamepad scratch pretty easily, due to the glossy plastic, even with a soft-cloth. Any recomendations on the best ways to clean it without scratching it or leaving marks?

@Izak80: I don't know how to answer your question about the Nintendo Network ID as I never used my Wii U often. But, in terms of cleaning the system:

I'd use a microfiber cloth. You could probably get away with dampening it slightly but if you do make sure to wipe it down with a dry micro fibre cloth after. I myself, will sometimes clean my consoles with some kind of good quality rubbing alcohol mixed with water. Some people might be against that idea. I'm pretty careful though.

If there is no Nintendo Network ID signed into the console, you should be able to sign it if you have an internet connection. It is also a good decision to link your Nintendo Network ID and your Nintendo Account at this link. https://accounts.nintendo.com/login?