98 SOHC Ticking

I just purchased a 98 4WD with the SOHC engine. It has 75k miles. I changed the oil and started hearing a ticking noise after short trips. I saw on some other boards about the Timing Chain cassete problem. Does anyone know if Ford will replace this? If they wont how long do you think this motor will last as is. It seems to run fine with plenty of power. Some people have said they seem to break at around 100k. Thanks