2003 Pontiac Grand Am timing and belt

Your vehicle has a timing chain not a belt, chains rarely fail but if it has gotten loose you will hear it rattling, if it has broken then engien will crank faster than normal but not start. Mileage is what you go by to do a tune up, if the vehicle is giving problems than it's too late for a tune up. Tune ups are meant to keep the vehicle running good before anything major happens. At 80,000 miles I would suggest replacing fuel filter, air filter and checking tire pressures and treads.