My daughter's are in GS (a senior and an ambassador) and I've been a parent volunteer for 10 years. If you have any more specific quesions, please pm me.
It can be a very rewarding experience for both you and your daughter. But it can also be very challenging and annoying at times, which is true of all organizations.
Added: Reading the other replies made me think of something. In our area they occassionally run "Daisy Days" or "GS sampler programs". It usually runs for 4 weeks, and both you and your daughter get the opportunity to see what meetings are really like and a chance to ask lots of questions. The one in our town had an employee of GS present, and my daughter actually planned and ran the meetings.
We (my daughters, myself and my hubby - yes hubby is a registered girl scout), have had some great times. My oldest is at the national convention in Houston. Her quote "Everything is amazing. I'm friends with a girl from Japan. I've learned more in one day here than in a whole week at school". That says a lot.
To be a leader, you will have to go through a series of training sessions. Your local council will assist you in setting up a troop and a meeting place. As a troop leader, you can make decissions as to how you want to run your troop. Also, keep in mind that it may seem overwhelming at first, but you don't have to do it all yourself. You will have a co-leader, you can ask the girl's parents for help, you can ask your service unit for help, you can ask older girls for assistance.
You'll never know unless you give it a try. If you feel that being a leader is not right for you, than become a parent volunteer.