The way the trip came about is pretty standard. Wilson was not an employee of the agency. He was a source. I would assume he had already been a source given his other foreign travel and dealings with Saddam, etc.
It sounds like it happened in the standard way--a reports officer was given the information and interviewed him after his trip. It would then be up to the reports officer to write the report and "grade" the value of the information, then disseminate it to the proper analysts, agencies, whatever would be appropriate.
The reports officer apparently testified that the info was pretty ho-hum and it received a routine distribution, i.e., not to Cheney's office directly. An analyst probably took the info and filed it for further use in his/her work.
I think it's a big sidetrack to argue about whether his wife sent him or not (though Wilson did lie about that). I don't think Wilson originally said that Cheney SENT him. He said that Cheney had to know about his report because his office wanted the info. Wilson's point being that Cheney knew he reported that the intel was bogus and Cheney still had that put into the SOTU.
It doesn't matter who sent him so much as it matters that Cheney did not see the report afterward, as alleged by Wilson, and the fact that the report actually supported the intel that Iraq was trying to buy yellowcake from Niger.
Just to finish my point, regardless of what Wilson said, some media accounts said or implied that Cheney sent Wilson to Niger, making his purported squelching of the report seem more unprincipled and sinister. On the other side, people who say that Wilson himself claimed Cheney sent him might have a hard time proving that, and might therefore lose a misplaced argument.
"Standard sources" don't have their trip expenses paid by the Agency.
And it DID matter if he was sent "by the Vice President" as he claimed (plenty of open sourcing on this issue showing Wilson lied) ....or not.
Being "sent by the Vice President" would open a few doors for him in Niger and give him an aura of authority in his dealings with the Nigeriens and the US Embassy in Niger...not to mention bolster Joe's importance to the Administration when he boasted about his Niger mission to journalists.
And make the Veep look like an idiot (Wilson's GOAL!!!).... for ostensibly sending a messenger to Niger and then ignoring his message.
This issue, I believe, was what got Scooter Libby involved and probably lathered up. "Who is this guy Wilson who is claiming he was sent to Niger by the Veep?"