Hi my 1997 nisan sentra has the service engine soon light on my mechanic says i may have to replace the timing belt soon is it worth it? i keep hearing a ticking sound and it only seems to be getting worst

A timing belt change is not monitored by the service engine soon light.it comes on when the computer detects a problem and sets a code.the code will have to be pulled to know what area to start to diagnose.the ticking could be anything from low or dirty oil needing to be changed to the valves may need adjusting,even a worn or dry belt can make a ticking sound.you don`t say how many miles are on the car or if you have changed the timing belt.if the mileage is over 100,000 kil(60,000 miles) then it should be changed.