questions regarding GC procedure

[Phee]

So I got married a couple of months ago and we filed the paper work August 30. I went for the biometrics September 30. And I looked online to check my case and it says they have received my paper work, and will schedule a date for our interview. My question, how long does it take to schedule an interview date? I know it differs from each case, I'm just looking for an estimation.
I also would like to know if anyone who was granted an ead card travel outside the USA? Did they have any problems when re-entering the US?
Any tips and suggestions to help with the interview? Would be highly grateful, we are super nervous.

Thanks in advance