I checked my '79 Argosy information and can't find definitive information on which cabinet contained the radio in the Minuet 6.0. If the radio wasn't purchased, it was typical in the 1970s Airstreams to leave the prewire at a specific spot where a hole could be drilled and the wires pulled through into the appropriate location. Since this is likely one of the differences between the '78 and '79 I would hesitate to say definitievely, but most typically the unit was in one or the other of the forward-most roof lockers (in my '78 it was the locker above the refrigerator). Hopefully, someone with a '79 will respond with how this was handled in their coach.
I haven't replaced the seals in mine, but do know that there is a detailed explanation in another thread here on the forums. A search for window seal replacement should turn up the thread -- Argosy has windows that are virtually identical to Airstreams of the same period. The one difference with the Minuet is that the side windows are acrylic and not glass.
The following link to Forum member balrgn's web site may be of help with the windows: Window Seal Replacement
Good luck with your investigation!