Yup, Richie Aprile was who Adriana was referring to when she was chatting with the FBI agents. He was her uncle. Tony explains his disappearance to people outside his inner circle by saying, "He went into the witness protection program."
As for who REALLY is a "mole", don't forget about capo Raymond Curto, who was revealed as a rat in episode 2 of season 3.
"Keep your body strong, your blood clean, and your mind sharp and mean." Henry Rollins
