My son found a guy working out of a storage building that recovered his seats. His wagon did not have a headliner in it. Had the bows but not the backing. There are no wagon headliners for old Chrysler products available so the guy tried to make one but it would not hold the shape. In the end, he apparently glued it to the metal which does not look as nice as factory, but, it looks a lot better than it did with nothing up there. Seat covers came out very nice.
Headliners can be pretty easy, or they can be really tough. Wagons are never going to be easy due to the size, if nothing else