Just came back from stamping at Newark. It is fairly simple. Take the document as zipper suggested.
Get the directions to broad street in newark. Once on the broad street if you are going North, tunr right on the E Kinney street and then left on the Orchard street. The parking is right there - $11 per day. Park there and you can walk into the building next to the parking which is USCIS and SSN building. On the front door the gaurds do some flow control so u may have to wait outside for a minute or 2. Go in, through the security check and go to 3rd floor. The lady there will check the Infopass and Id and guide you to the line. Stand in line, when you go to the window, the lady there will take your signature and index finger print on a form. She will take the approval notice of 485 and staple the form, Infopass and approval notice together and give a token. Every member in the family needs separate Infopass. DO NOT FILL THE FORM. Just keep tham as it is as they gave you.
Now they will ask you to wait till called by the token number. Go to that window, th eperson will take all documents and photos from you, do the paperwork and ask you to wait for passport.
Now you wait again and after some time a lady will come out from a door and call names of people and hand them over the stamped passport.
It took a while to get the stamping done. Went in at 8:30 and was out by 12:30. Had lunch in the 2nd floor cafetaria than.
Best Of Luck.