Don't know if its too late and you're already en-route Wimpy, but I wish you luck.

IME I've had to be very careful about upgrading an itinerary before it’s ticketed. Not with regards to the fare charged, but to the fact that the system seems to choke completely when I try this. I get a call from my travel people stating that they can't ticket my reservation since its been changed from the original to an upgraded res. I usually get ticketed through my corporate agent so I don't know if your method would yield different results.

I've got a reservation booked for 8 days from now and I'm forced to wait to put in for the upgrade because my agent is so slow to ticket - there's a holiday tomorrow in the US. It makes the upgrade roulette waiting game a lot more painful.