I also visited there. Bus is not expensive, from chengdu to jiuzhaigou directly, cost about 100 rmb, maybe more now. yes 12 hour on the way, it's long but the view is great if you travel in day time, but I took the night bus last time, on about 8am I got there.
try to avoid the crowd! take your time to wander on the beautiful forest or ley and the peace. the entrance ticket is expensive, including the environmental-protection bus inside the park.
then... I'd recommend the Mounigou near Songpan county. search for "Shunjiang" or "Happy trail" you'll find some nice travel logs.
bus is safe, the drivers won't be like maniacs
