IIRC, it has been brought up here before, so worth a search. Again IIRC, it's a good thing that your dealer mentioned the diff oil change as many don't/have absolutely no idea that this might be a good thing.
Will certainly mention it to mine as if a lack of an oil change means it does go wonky at 3 & a bit years, I don't doubt it is not a cheap fix

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I'll be not too far away from my second change by your age of car (assuming I still have it), so could be worse!