DL Skymiles agents will NOT "deal with" itns booked as part of a DL Vacation. When I tried to upgrade to D1 on a DL Vacation booking in progress, the agent noted: "we don't deal with GUC...you have to call DL Skymiles". "Hidden" away in the GUC rules: to use a GUC with a DL Vacation booking call 1-800-800-1504 (DL Vac. phone number
); it took nearly 1/2 an hour to sort things out.
(for the delay),
(that even worked....)