First Time PSP Buyer [Living in Japan], caveats!? help me!

Hi guys, i'm new to the community and am having these doubts about buying a psp for christmas (ps: i already have a GP2X, so i have already caught the homebrew fever, just want more power :P)

the points are: [warning: extreme newb questions ahead :)]

1- i live in Japan, usually here, when a new model/latest firmware of anything is released, all the old models/old firmware machines are removed from stores QUICKLY and replaced with the newer stuff... so usually everything is at the highest version, i don't have checked the stores yet and i don't know if the psp phat and slim are still being made in parallel [haven't read the news :(], so : how can i buy a psp and be safe that i'll be able to put a CFW in it? caveats on models or mobos or whatever? buying tips?

i have a friend or two here that heve a psp with cfw in it, so i think i'll be able to produce the pandora's battery [did a little check up on that but don't know all the details] if that's needed.

2-i realize that the majority of the community is from english speaking countries, so people don't mess too much with Jap PSPs, the question is : are the worldwide psp's standardized? like, will i be able to use all the tools and stuff here on a jap psp?? any version to search [if you read question"1" you'll know i'll only have the newest models/mobos/versions available :(]

3-do i write too much? Yes. :rofl:

thanks in advance, waiting eagerly for some newb-enlightening answers...