As a Delta PM you are now eligible for free upgrades to FC. This has happened just in the last month. NW does not show an "upgrade requested" on their system. It is all automated and refered as the "EUA" or Elite Upgrade Automation and if you clear your upgrade ahead of time (for PM it would hopefully be 5 days before the flight) you will receive an email or something and it will be reflected on your reservation.

As for selecting a prefered seat in coach, that has been a perk for a long time based on being SkyTeam elite. After you purchase the ticket, assuming you enter you Delta SkyMiles #, the NW system should see that you are Elite and will list you as "Platinum Elite" on the reservation and you should be able to select the prefered seats (but NOT the Coach Choice seats, those will have "$" on them in the seat map).

If you are unable to select the "P" seats then contact NW and they should be able to fix it.