Agility training

Hello, everybody,

We recently adopted a mixed breed puppy. Her mother is a Boxer/German Shepherd mix.
Her father is an Australian Shepherd. She is a very active, high energy pup who loves to carry things around. All I know about agility training is the competitions I have seen on TV. I would like to find an activity to channel all that energy, I would appreciate hearing from someone who has partricipated.

Are mixed breeds allowed to participate in formal events? How old should a puppy be before starting? What kind of equiptment do you need to start training. Any advice would really help.