[JohnBraden]

Tourists don't need a visa to get into Japan from most countries. I don't know where you're coming from. US citizens get a 90 day permit stamped on your passport.

If you want to fly JAL you can. I always do, but there are other alternatives that are cheaper.

I guess you can stay at a capsule hotel, but there are hotels in Tokyo that are quite reasonable.... one has to research it.

There is a roller coaster across the street from Tokyo Dome, if that's the one you were asking about, but the day I was there in October, it wasn't running....

As far as finances, it all depends on what you're planning to do. Credit cards aren't used as much as they are in the states (here again, I'm supposing you're in the US). You can withdraw cash at ATMs as you use up your funds, I guess. I brought it all with me in the form of TCs, so I cashed them in as I saw fit.

Have you looked at other threads in this forum? There are quite a few threads about this very topic.