I think this thread really belongs in the Delta SkyMiles forum, since it is a DL benefit...

But yes, you will be able to enter your Delta SkyMiles number and you should be able to choose exit row seats. Although, you sometimes have to leave the reservation and then recall it again before it recognizes that you can choose elite seating (like the old NWA system).

It's a benefit that you are entitled to, so if it doesn't work you can always call Alaska and they will move you (1-800-ALASKA-AIR). I think you'll find they are much more friendly and helpful than the people at the DL call center.