Beethoven Leonore Overture No. 3

[fluffehkitteh]

Hello!
I'm not normally one for posting topics/replying, but I've come across a few questions that I can't go to my teacher for.

I'm auditioning for my university's wind ensemble (I just transferred into a university school of music from a college music diploma) and my teacher (the same teacher that taught me in college also teaches at the university and will be my teacher this year.) is the one who does the auditions. She can't be bias for the audition so I can't go to her for help on the excerpts.

Most of them I have minimal to no problems with, but for some reason, I cannot for the life of me get the Beethoven Leonore Overture No. 3. Our excerpt is the beginning of the piece to measure 25 (beat one) and measure 328-360.

Opening:
Breathing. I can't take the opening without extra breath. Does anyone have suggestions for breathing exercises that I could use to increase my capacity?

328-360:
This part is mostly fine except, again, the breathing at the end. I've tried everything I can think of to get through the 8 1/2 measures of holding a high D and pretty much always fall short around the 6 1/2 - 7 mark.

Any help is appreciated!
Thanks!