Oyama? In Itabashi City in Tokyo?
Then, this "O" is pronounced long, and the station which you mention is likely to be Oyama Station of Tobu Railway.
(There are at least 3 railroad stations in Japan whose name can be spelled as Oyama.) I need to get two suitcases and myself to Narita Airport by 7 am from Oyama the Narita Express runs from 6.15 so that would be perfect
No; even the earliest JR Narita Express train does not arrive before 7 at the stations in the airport.
It sounds better to go on the previous day to the airport or a nearby place;
if that day is a weekday, I recommend you avoid rush hours in the morning and the evening.
How is your flight scheduled?
Currently there is no station in Terminal 3 of NRT;
when your flight uses Terminal 3 and you take a train to the airport,
you disembark at the station in Terminal 2 then head to Terminal 3 by bus or on foot.
While the Ikebukuro Station complex is huge,
just near Tobu central gates (for Tobu Tojo Line) are
JR central gates and a Tokyo Metro gate for Marunouchi Line.
One option of transportation is to go
by Tobu Tojo Line to Ikebukuro
(150 yen per adult),
by Tokyo Metro Marunouchi Line from Ikebukuro (M-25) to (M-16) Ginza
(200 yen per adult, about 20 minutes)
then by the Access Narita bus to any of the three Narita Airport terminals
(1000 yen per adult (except: 2000 yen for a few late night buses )).
- JR-East: Map of Ikebukuro Station http://www.jreast.co.jp/e/stations/e108.html
- The Access Narita http://accessnarita.jp/en/home/#timetable-title-3384
Regarding this bus line:
for about 15 seats per car, your ride may be reserved;
the other seats are for rides without reservation.
One possible demerit is that the reservation is acceptable only via the website and in Japanese.
Buses depart frequently for Narita Airport and the Ginza bus stop is the starting point, so I suppose you would catch one on the spot.
The Ginza bus stop is above the Marunouchi Line tracks, near the elevator between Exits C5 and C7 of Ginza Station.