You will need some cash, because credit cards are not as commonly
used in Japan as in other countries. But you can conveniently exchange
money at the airport.

Here's a description who to get from the airport to the faculty house:

Don't even think of taking a taxi, the airport is about 70km from
the guest house. There are convenient buses and trains, and they 
cost 3000Yen per person.
When you leave the customs at Narita, you are
in a hall where you can buy bus or train tickets, and the staff will tell
you where to board the bus or train. Everything will be explained,
punctual and well-organized, so relax.

Bus: The fastest way is to take a direct bus to SHIBUYA  (it has 
two stops, take the second and last one: Shibuya Excel hotel). 
Then you just have to walk down two floors to  the local train you need 
to take, see below.
There are buses at 
13:05, 14:05, 15:05, 15:30, 16:05, 16:30, 17:05, 17:30,18:05, 20:05, 21:05. 
It should work for most of you.
link

Train: There is a direct train to Shibuya, Narita express. 
There are trains at 
16:15, 16:45,   17:14, 18:14, 18:46, and 19:13. 
link

A cheaper alternative is Keisei Skyliner, which also has more trains
and different hours. The disadvantage is that you have to change trains one
more time: 
Take Keisei Skyliner to Nippori, change to JR Yamenotesen, and then go to 
Shibuya.
link

After arriving in Shibuya: You have to find 

INOKASHIRASEN (i.e. inokashira-line).

The good news is that  it's the terminal station, so you cannot go 
the wrong direction. The bad news is that there at least 9 different lines
meeting in Shibuya. If you took the bus, just take the stairs down,
if you took the train, follow the signs or ask someone.

After you find the entrance, buy the cheapest ticket for 120 Yen
at a ticket vending machine (which have an English menue). 
Enter through the gate, and board a train. DO NOT board an express train. 
The trains run every 10 minutes, so no need to hurry. 
On the local train, take the second stop:

KOMABATODAIMAE

Take the east exit (where you have to walk up stairs), exit the ticket gate
turn left and walk down the stairs. You should be in front of the main
gate of Tokyo University. Turn left at the gate, walk about 150m until you 
reach a french restaurant. The entrance to the guest house is on the right
back of the building. Once you are on campus, you could also ask the 
officers at the main gate for help.