The PSP-3000 can access the PSN, yes.
You need the PSN one way or another, either you buy them directly using the PSN option on the PSP, or you install Media GO!, buy the games there and use it to transfer them over USB cable.
$130
no
no to the ps3 though
$145
Yes :D
You can't do it.
348 dollars
no the pspgo
No when the games and the PSPNGP come out they will not work in the PSP
No, a Japanese PSN account can only be funded with a Japanese PSN card, one with a yen amount on it.
It's actually known as a PSN ID. http://www.us.playstation.com/PSN/mediago