I realized as I was finishing up the anime that they never showed the actual reattaching of Naruto's arm unless I missed it somehow. Or did they skip all that?
They inferred the part where they grew him a new arm. Naruto states that he got a new arm, from the 1st hokage's cells But no they do not show it in the anime. I also do not believe they showed it in the manga. He was in the hospital, then an episode or two later he is showed talking with Sasuke, where Sasuke deigns not to get a new arm.