You are arriving on which flight? On a week day or weekend?
I do not recommend taking a regular 'tokkyu/kyuko' from NRT, be it T1 or T2, in the early morning on a week day. It gets so crowded and if you have big baggage, you will be frowned on. These trains will be jampacked as it nears Tokyo (and early morning trains don't go to Nippori.)
Early morning Skyliers are non-reserve seat 'morning' liners but I think they are better than regular trains.
You can just go to a ticketing counter for Keisei and buy a ticket through to Shinjuku. Just tell them that you want to change trains at Nippori and go to Shinjuku.
Two up escalators are available at Nippori. No down escalators for Yamanote Lines. But transfers at this station is very easy, as other posters say.