When I was a teenager (many moons ago), a group of friends and I went to a salon in the Empire State Building that offered to do our hair and possibly use us in a styling magazine. It was also a training day. There was five of us. Three came out beautiful, 2 came out looking like boys ( they cut our hair extremely short). At the time I was pissed. I wanted the good hair cut and photo op. When we think back now though, it was a blast. We all got complete makeovers for free and hey 3 out of 5 isn't bad odds.
My advise is do it. Just tell them exactly what you want and "don't want". Have fun and good luck!!!