No interview is required to my case. It's my understanding that the background checking is completed after reviewing my fingerprint result I submitted before. The Approve Notice I am going to receive will instruct me to have my passport stamped (I151) as I was advised by my attorney and friends who had similar experience. Normally,if nothing's out of blue, it'll take another 3-8 weeks to receive the GC in the mail from the date your passport's stamped.
Good luck.