I *think* you can ignore the exact details of how he found out who she was (her exact name, etc.). That's not at issue in the indictments. He was told by multiple official sources in June 2003 that Wilson's wife worked in the CIA.
The whole key to this thing is what he told the FBI and the GJ. He told the FBI that he was surprised by Russert asking about Wilson's wife. Surprised in that he, Libby, did not know she worked for the CIA. Apparently, Russert never asked about Wilson's wife.
Ah, okay thanks.