When you get the game, the system will tell you if you have to update it or not. Normally, when you get a brand new game there are a few updates you have to get but I wouldn't worry about it too much. Only takes a few minutes.
Ooo those updates. I hate them so much they take a lot longer on my 3DS then it should. And don't let me get started about updates on the PS3. *shake fist in the air*
There are some people who have wifi, and some people who don't. To update, you must have wifi. It wouldn't be fair to those who don't have wifi. So, I'd assume that you don't have to update. Besides, in mariokart7 you had to update the GAME to play with wifi, not the system.