i wouldn't count on epass working there. it took me a long time before i could find an atm that would take my card. they have their own atm/bank networks, and only a few are compatible with the networks we use. credit card usage isnt really common there either
forget about getting a cell phone you can tether. foreigners can only buy the overpriced phones/sim cards they sell at the airport that charge an exorbitant rate for data use.
just about everything there is to know can be found here though:
http://wikitravel.org/en/Tokyo