Well, if you are applying for k1 visa then you can go ahead and pay the visa fee, do your medical exam and schedule an appointment. Also, they do not send you packet 3 or 4, they will just send you an email stating that nvc forwarded your case. They will also mail you that letter which reaches after a month or so. Do not wait for that letter, you can just print it from your email. When you schedule your appoinment, they will send you confirmation page with things that you need to provide. I have just been through the whole process of k1 visa so I am aware of recent process. If you have any questions, don't hesitate to ask. Good luck.
