I have a 2018 Mazda 6 and I'm looking for people with experience in it.

Question one: Is it better to change the oil for my Mazda 6 if the first owner already changed it slightly after 100,000 km, and now the car has reached 200,000 km and I'm not sure whether I should do the second oil change or not. Question two: Where would you recommend I get the oil changed in Al-Jubail? And if there are better options in Dammam, where would you suggest? I know there's a workshop in Al-Jubail that only services Mazdas, and they said they can change the oil, but they don't guarantee anything. Question three: Would you recommend changing it at companies like Petromin, since I heard they provide a guarantee? Note: Occasionally, a slight vibration occurs, sometimes slightly stronger, between 20 and 30 km/h after driving for a while. Anyone with experience, please advise me here or contact me at my number. I've only owned the car for two months, and the car is excellent, thank God. I'm afraid to change the transmission oil and then regret it. What do you suggest? 0536069990