I asked a similar question about the batteries on this forum and did not get any replies. When i bought the galleria the dealer told me they were sealed batteries and didn't need to be refilled but the same person told me the refrigerator runs off of propane, which is not true. I wonder if there is someone at Coachmen that has good information on the Galleria.
Mine was a 2016 leftover so it was new, there wasn't a manual for it until later. I had the dealer winterize it last year, but I'll give it a shot this weekend.
One coach battery failed last year, but was replace under warranty. I've found that the Forrest river team is very responsive to emails, I was just trying to use the forum, but there isn't a lot of owners of the Galleria I guess.