from NRT, take Keisei to Ueno station and change to the subway Ginza line to ginza station.
Exit station, walk east 5 blocks (?)... tsukiji-sushiko on right side
This is a high quality place that has a cheap lunch set menu -- only 1000 yen last week
http://www.tsukiji-sushiko.com/shop/SUSH_E0101.htm
After eating you can walk to Ueno station in 70 minutes.