Yes, battery replacements & Other services are done here, I've Had A Couple Buttery Replacements Done There No Problem!
They do some repairs in the store and for ones they cannot handle there they send the watch out.
I don't know if the guys in there are G-shock experts. I think they're just sales guys. Personally I would call first and find out to risk a wasted trip. Best thing to do is look up in a forum or YouTube how to do it by for your specific model.
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