[Cyclamen]

It's very easy to get to Zepp Tokyo. Just hop out from the Yamanote-sen at Osaki, jump on the Rinkai-sen (the train going to Odaiba) to Tokyo Terepoto Eki. Or exit at Aomi eki from the Yurikamome-sen. It's a good place, but a bit too small for huge events...
The Yamanote sen is very comfortable, and you can get from Osaki in around half an hour to Ueno, Shibuya and Shinjuku. Because of this, there's no need to find an accomodation near to Zepp. Every hotel on the Yamanote would be ok. A one-way ticket on the yamanote is around 190yen, the trip on the rinkai or the yurikamome will be 350yen.
To get from Narita to Tokyo, take a local train to Tokyo Station (arond 1700yen) or the Limousine Bus to Shinjuku (3000yen), both stops are connected with the Yamanote line.
If you're planning to stay there just one night, why don't you plan on spending the night into a karaoke? It will cost you around 2000yen, and you don't have to sing all the night, you can confortably sleep on the soft couch!!
As for meals, look for a Lotteria, or a local Soba/Ramen/Curry shop. You'll get an excellent meal for around 500yen. But you could also go to a konbini and but a bento (lunch in a box!) and some other stuff (onigiri, nikuman, sandwiches, melon pan, sweets or drinks), with 1000yen you'll be more than filled!