File I-485, ask for help!

My I-140 has been approved. I want to file I-485 by myself. I have several questions ask for everybody.

1. There are 3 people in our family. Me, my wife and 11 year old son. How many I-485 form should I fill.

2. How to caculate the filing fee and fingerprint fee?

3. Should I send one money order or make them separate?

I am waiting for your kind answers. Thanks in advance.