EASIEST way to get to the TH from NRT and to get from Tokyo Bay (which, I agree with the other posters, is in a lousy location except for Disneyland) to NRT is to take the "Friendly Airport Limousine" which is a bus, not a limousine, and is not exceptionally friendly. The hotel can book your return trip.

Easiest way to get from the TH to the TokyoBay Hilton? There isn't any. Taxi will be quite pricey, at least Y10,000, maybe noticeably more, in my opinion. The way using public transportation that involves the least walking is to take the JR Rinkai train line from Shinjuku station to Shin-kiba station, then transfer to the JR Keiyo train line to Maihama station where Tokyo Disneyland is.

Rinkai line trains run about every 20 minutes during the day and leave from track 1, 2, 3, or 4 (it varies) at Shinjuku station. Enter through the minami (south) entrance or the shin-minami (new south) entrance.