1999 Nissan Sentra Timing Chain

Engine Mechanical problem
1999 Nissan Sentra 4 cyl Two Wheel Drive Automatic

Hi. Got this car from my mom. She didn't change the oil all that frequently. Hear a rattling noise, was told it was the timing chain. Now, while on the interstate, driving 70 mph, the car starts to lag, then accelerate, lag then accelerate. It's intermittent. I'm thinking this is the timing chain. If so, the car is 11 years old but has only 54,000 miles on it but was not cared for properly. Is it worth it to fix it. If so, how much would I expect to pay? Thanks.