We finally finished off the last steps toward getting my wife permanent resident status in the US.

The lady at the Consulate told us a few things that sounded a bit odd to me. If any of you have such experiences, I would really love your input!

Arrival
We have to present the unopened packet at the passport control. The officer will give her a stamp indicating that she can legally live and work in the US.
However, the lady told us that we need to ask for a 2nd stamp to be able to leave the country. Also, she said that it could take 1-3 hours to clear immigration upon arrival.

Is this common? Silly me was hoping that since the Consulate approved the paperwork, we could trade the packet in for a stamp and be on our merry way. What generally happens that requires such a wait?

Actual card
According to the immigration web site, it takes 8-10 weeks to receive one's greencard. The lady at the consulate told us one year.
Which is more accurate?

Thanks for any help to these questions!