dealer was correct

check your car manual. in the service schedule section, it should say what need to be serviced. For many later year VW cars, trnnies are sealed, not for services. if indeed you find something abnormal, dealer will open it up and r/r, the cost is high (close for a new tranny).

if your car has the timing belt, 90kmi is about the life of it (again check manual). for japanese cars, around $300 - 400 some shops will do tb with a new wp; for euro cars, it will cost more. (find a "dealer alternative" to do it, save you money).