The Australian was promoted from the coaching set-up to the top job after director of coaching Kidney left in May take charge of the national side.
Despite the upheaval, O'Gara expects the European Cup champions to flourish in the new era.
He told the Irish Examiner: "We will miss Declan (Kidney) for all of the things he brings to the game, for the things he brought to Munster.
"But Tony is a very good technical coach, and I think the age-profile of this squad is such that we're ripe to benefit from his type of technical coaching."
He insisted McGahan will have 100% support. He added: "There are no barriers in this Munster squad. It's not an issue; honesty prevails throughout and that will always be the way. It will never change."