http://www.cornellurology.com/uro/cornell/pediatrics/genitoplasty.shtml

Here is a web site from Cornell University (urology) that explains the surgery and the ultrasounds needed.  I would think ultrasound would be less invasive.

I agree with stacey - I would not regret the surgery or procedures.  She is very much female but I do think an experienced doctor is needed.  If I had a daughter with CAH that needed surgery - I would go to Cornell University or somewhere that is KNOWN for the surgery and not just someone that wants to try their skills out on my child.