You can forward your heavy or larger stuff and hand carry the necessities for the first night using the luggage delivery services at Narita Airport. Though I'm not sure if you can get same day luggage forwarding (usually it arrives next day), I guess it depends on what time you get there?

As for hourly departing trains to Chiba, you'll have to take the JR Rapid (not the Narita Express (unless you're arriving sometime before 9am) and not the Keisei Line).

The timetable for the JR Rapid from NRT T1 is: 07:00, 07:57, 09:04, 10:00, 11:00, 12:00, 13:00, 14:00, 15:00, 16:00, 17:00, 18:00, 18:29, 19:01, 20:07, 21:14, 22:16

It takes about 42 minutes to reach Chiba Station, at Chiba Station change to the Sotobo Line to Mobara, and that's about another 40 minutes.

Totally the ticket is 1280 yen, you can purchase direct from the JR vending machine at Narita Airport. At the machine Press the button that says 1280 and insert cash, get any change, pretty strait forward you don't even need to hit the ENGLISH translation button.