They will again service by regional area the 1st week of May 2011 see related question
No, PSN is free and there is no indication that is going to change.
500 how are you going to find
Yes, rumors are that PSN will be back online May 31 Source: Sony
Yes, sometime next week.
Yes, it can happen, but it happens indirectly. Using the modded PSP can get the associated PSN banned, and that ban applies to anything that tries to log in to that PSN account. So an associated PS3 will find itself suspended from the PSN too if it uses that account.
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
It's working now and has been since it restarted on June 2 2011
The PSP-3000 can access the PSN, yes.
WHAT DOES PSN STAND FOR OR MEAN
by PSN you need a account to PSN
You can't. PSN stands for PlayStation Network. You can't connect a DS to PSN.