richtom

I just finished 8 "Millie" shows on lead and I can verify that Tony is 100% right on the range issue. It tops out at high E, but there is a very exposed attack on one of those E's, so be ready to jump on it.
The lead part is rather active and you'll be doing flutter-tongue, growling, and plenty of whaa-whaa. Lots of the mentioned "ricky-ticky" jazz/dixieland stuff from the 20s, but it is a kick to play.
I did have to do Saturday matinee' and evening perfomances and endurance did come into play at the end of the evening performance, but it was tolerable and do-able.
We had a second trumpet on only 4 of the shows and the horn player did some doubling on 3rd trumpet. You may need to play some of 2nd trumpet cues, but the licks are not hard.
We used the Broadway score and had a very small orchestra with 1 violin, 4 to 5 reeds - depending on who could make it - keyboard, percussion, bass and trombone as well and the trumpets mentioned above.
Even if you can see the stage, you'll be very busy counting and playing, so you'll miss out on some of the stage fun.
Enjoy it. You'll be glad you played it.
Regards,
Rich Tomasek