First of all welcome to flyertalk and the US forum. You will find some of the most knowledgeable people in the world here when it comes to anything about points and miles. We look forward to seeing you here often.

The answers given above are correct, so get to the airport early and ask. You may also want to consider keeping row three on the way back. I personally prefer row 1 going over and row 3 coming back. Unless you are planning on sleeping on the way back, I find the seats in the second cabin more comfortable for just sitting and watching a movie, etc.