Sort of follow up:
After 10 tries I got through to DL Vacations 800# (busy, call didn't go through etc. messages) and 2 hours on hold

, DL is having an issue with synchronizing with DL Vacations mainly on
www.delta.com.
I have 2 DL Vacation itns, one just had a flt change--both show no seat maps and imply that I'm flying on a "partner" airline. Since my first itn is in late May hopefully things get sorted out by then. DL Vacations use "exception" MQD method, plus accelerator bonus have higher value than regular ticketing and at a lower cost.