Welcome! Just follow the crowd... generally the japanese will have a separate line at immigration/customs, so follow the non japanese looking crowd.
Dont be worried! If you get lost, it just adds to part of the fun!
If you are worried about getting a little lost, its always nice to have an address written in Japanese that you can show to the taxi driver... I didnt do that in Japan, but I have in other countries.
I know nothing about the buses in Tokyo, so I will watch for the information that arises also.