If you were asked before

they sent you the green card, you have to. If you were not asked, the INS would just send you the card directly. In this case, I think you don't have to do so. I was asked to have the passport stamped, and at the same time, turn in all the I94, EADs and AP.

My friend got another experience, he got the card directly without stamping.

And the other day I found out that I didn't turn in one of our old EAD, I think they won't care about that so seriously.