Hi!
I don't know where all those places are BUT,
If you are going by yourself and you dont speak or read Japanese, or if you don't have a friend in Japan I think you will find it VERY difficult to go somewhere worthwhile! Its not like Australia where you can just pack up and go out for the day, in Japan you need serious planning lol!
Best thing to do is if your going for a Month get a 3 week JR(japan Rail and 3 weeks is the longest u can get) ticket, i think it costs like 300 bucks or something. Otherwise all your money will go on transport. Also if you have not lived in Japan before I would pretty much forget about a hire car - lets just say the Japanese road system is one F@cked up system. They dont have street names either.
You really need someone that can SHOW you where everything is, or someone that can write very detailed maps.
Good places to go other then what you mentioned - Akihabara - electric City- north of tokyo,
Hakone - 2hours south west of tokyo - Drift heaven, Roppongi - West of tokyo - Party City!
I may be heading over in Late April as well, if so I will let you know and perhaps I can show you some places East of Tokyo. My friend owns a dealership over there (He is Japanese) so he knows a lot of choice places! Although there is a larger police presence in that area over the last 2 years to stop drifters and bousou.
Cheers, sorry I couldn't be more helpful.
PS. If you get a Options mag soon as you hit the Japan, and u can read some Jap, then it has some maps to some tune shops, plus it also has addresses of some second hand shops.