There is a lot of good information within the Japan subforum for you, have a good read.
In a nutshell, $3400 was a rough price from a few years ago which included return flights to Tokyo, taxes, insurance, accomodation for around 12 nights, and rail pass. Where you want to stay in terms of proximity to Tokyo, and the quality of the place you choose to stay will dictate what your paying per night.
Regarding stores, Super Autobacs is great for a look if you have never been there before, the Tokyo Bay store is one of the more impressive with the Tommy Kaira dealership out front, but is is very expensive and the stores generally don't carry much in the way of actual performance parts in stock, most is order only.
Seeing some street Drifting, well that depends if you have any contacts that know the scene and can drive you around as without knowing anyone, or knowing your way around Tokyo, and not having a car, the chances of you stumbling across some drifting of an evening are virtually zero.
Give us some idea of your budget and how long you intend to be there for and either myself or one of the other regulars can give you some more information that might help you