Marlboro,
I didn't read the other posts cause I've been where you are. There are attorneys that deal specifically with the father and know how to protect your right and make sure that you dont get screwed. As far as how much you need to pay, they look at your potential earnings and that of your ex and determine what you need to pay. Do a search on the net for the fathers advocates/lawyers they will help you with atty fees as well. From here on out document EVERYTHING that takes place between you and your ex. Good luck!