Why not send an email to the dealer and explain about the oil change allready been taken care of, and then ask if they would suggest whether to take the service enroute, according to milage, or wait until you return and then take the service at the dealer, knowing that the milage has been exceeded while oil change is taken care of...
Getting an answer in writing may be worthwhile in case of any milage dispute vs extended warranty...
As for resetting the service, why not go to manual settings and extend the date to a time beyond your return, and the milage to a distance slightly more than expexted for the return.