How concerned should I be about 100,000/timing chain replacement?

Hello, this engine has a timing chain.Timing chains are usually in place for the life of the engine. They do not typically "break". Your father-in-law is speaking of timing belts, which can break due to mileage and age. This is not the case with your vehicle. Now - on rare occasion, with a lack of regular oil and filter changes every 5,000 miles or so, the timing chain can get stretched on these vehicles, causing noise and performance issues. This is not typical, but I have definitely seen it a few times. But, as long as you keep the oil changed, your chain will most likely be in place for the life of the engine...and no repairs or servicing is needed for it.