I'd be more excited for the production if it starred Kevin Kline instead of Peter Gallagher. They're around the same age (59-66 respectively), however, isn't that kind of old for Oscar anyway?
Peter Gallagher is 59, but a "young" 59 in my opinion. John Cullum was in his late 40s when he starred in the original stage musical. John Barrymore was 52 when he did the film.
I'm not bothered by Gallagher's age. Oscar Jaffe was Lily's "mentor", Svengali even, as well as lover. I expect him to be nearly a generation older than she. Kristin Chenoweth will be roughly 47 by opening night.
I saw the original. Remembered enjoying it but do not remember details . Musically I think it is type of an operetta. Seeing one of the first 4 previews upstairs.