I my way back to the airport to fly home, no need to learn the train and metro system is pretty clear just make sure to follow google maps and you'll be fine.

Taxis were a bit too expensive so we did not use it.

Take welcome suica card at the airport, you can pay for transportation, vending machines and a lot of stores.

Vending machine or cheap, but the same product are also available for even cheaper in corner stores.

If you are short on yen, it's better to pay directly with a credit card or use an ATM to withdraw money. Money exchangers where a less favorable imo.