No worries hun!

Im not a doula but i have one for this birth (when ever that will be..LOL).

I also has a student for DD2.

To answer some of your questions (from my experiances).

Will she want to watch the business end of things???
If you dont want her to....say so. Last time i made my doula the photo taker as well...so she was down there and to this day she is forever greatful i allowed it. I was her first mum so it was new for her. I never felt uncomfortable with her being down there either.

Do doula's perform internals?
Nope they dont

Will she be able to give me advice about what pain relief is available, and what has the minimal impact on my baby?
She will definately be able to help you out. Let her know what kind of pain threshold you have, what you would liek to see happen/not happen (eg....i dont want drugs and i know i ask for them in a peak of a cx and she is aware of this so will try get me to focus on the pain and then when the cx stops re-ask if i do really want it).