round-trip travel from nanjing railway station to China Dinosaur Park, Changzhou in one day

I want to visit China Dinosaur Park, Changzhou in the morning from NJ railway station and return in the evening. How can I make it easy to go for the round-trip journey? I don't want to go through any travel agent. Can I get the train ticket at the same time of travel? I want to make this tour during labour's day holiday, will it be good or any weekend will be better? Kindly suggest me about the train, city buses and others required information about how to reach there and return back in detail. Thank you in advance.

Jay