When Vince Gill walked on the Grand Ole Opry stage last night in the middle of Rascal Flatts' set, the boys may have been surprised.  But even more so when he invited them to become the newest members of the legendary country music institution.   "We had absolutely no clue," a still-astonished bassist Jay DeMarcus said backstage. "The only thing that was a little bit weird to me was that I told my wife to stay home tonight. I said, 'We're only doing three songs; it's a short segment.' And she showed up right before we went onstage. She said, 'I put the baby to bed and the nurse was there, so I just came on.' And even when Vince came out, I thought he was just messin' with Joe Don (Rooney)!"    The CMA Vocal Group of the Year nominee's 11 year career has earned them tons of honors, but the Opry invitation has always been at the top of Gary LeVox, Jay and Joe Don's list.    "It all hit me, a flood of emotions all at once, and it was tough to keep it together"  Jay says.   Read about it here. Before them, the newest members of the Opry were the Oak Ridge Boys and Blake Shelton.  The induction ceremony happens October 8th.  Before then on October 4th, the Opry plays host to an all star tribute to Randy Travis.   http://www.youtube.com/watch?v=L4MjY_X9wiU