I have a 2005 Ford Focus with a 2.0L engine. I am not having any problems with my car but I have just hit 98K miles. Do I need to worry about replacing the timing chain due to the mileage?
No. You have a timing chain (not a timing belt). The timing chain should last the lifetime of your car.
No. You do not need to replace the chain. This is one of the nice things about timing chains; they do not require periodic replacement. The timing chain should last the life of the engine.
Timing chains DO need replacing..but not for at least 250k miles. For some that's the life of the engine. And one nice things about chains is they will make a lot of noise before they break.