Intervals for timing belt and fluid exchange

Hello dear friends. I have a very real question. How much km is the timing belt and fluid change at 4.2L? and above all what are ribbed belts and how often do they have to be replaced. wants to buy a v8, which already has 228,300 km on it, but is supposed to have been kept very well and checkbooked. the owner changed the timing belts at 120,000 and visited several workshops and inspections were allegedly no more timing belts were required? can you buy that from the seller? because otherwise he makes a reasonable impression and the car should be the father-in-law of the seller. I would be very pleased about an assistance position like in the "buy help". thank you in advance, your mark.