I bit the bullet and called AC again. At 11pm PDT the wait was only 9 minutes.
The agent was super helpful and was able to get me the seats I generally wanted on SEA-YVR and YVR-LHR and back. They denied me access to the single seat "K" side of a 777-300W because it's reserved for Altitude members. At least I am no longer sitting in the aisle in row 1 near the galley. If I'm stuck in an aisle I'll take the middle of the plane which should be quieter. They were also able to email me a copy of the itinerary showing the new seat assignments.
What's even cooler is United.com is already updated with the new seat assignments that AC gave me. Great "talking" between the two computers...when it works.
-RM