Day trip to Dazu starting from Chongqing

I plan to visit Dazu in a day trip starting from Chongqing. How many time will be necessary to do this? Everithing will be OK if I will use the public transportantion to reach the Dazu and surrounding or it is recomended to arrange a travel agent? In Dazu all the places are open to public or some of them are closed. Could be visited all the places in half day? Thank you very much. John