For those of you who have not been to Brazil, a galeria is an enclosed area of shops with an open entrance. Often there will be one or two floors of shops then above them multiple floors of apartments. Not dedicated shopping like a mall and not individual shop outdoor entrances like a shopping center. Some are dedicated to a particular kind of merchandise like electronics or women's clothes. Vendors rent individual booths or stalls.
Honestly it doesn't sound good to me....
"Have been to" is like "have visited", "have been there at least once (and left)"
That suits sentences with "já", it suits sentences about visiting countries, but it does not seem to suit this sentence.
Somehow, "já" twists the "motion" verb "ir" to a "presence" meaning because it implies a past and completed "visit".
Usual possibilities for "have/had been to" in regular sentences are "(ele) esteve / tinha estado".
Perhaps, one could argue about "ido à galeria", since "a" can denote a short/quick stay while "para" sounds more permanent.
- Ele já tinha ido à galeria antes = He had already been to the gallery before ("já + antes" makes it a "visit" - sometimes "antes" is implied)
- Ele tinha ido para a galeria = He had gone to the gallery (standard meaning of "ir").
- Ele tinha ido à galeria (this is arguable, but certainly it can be "had gone").