Symptoms to replace Timing Chain

It doesn't need to be replaced due to high mileage, it is not typically a maintenance item like a timing belt would be. The symptom of a failing(failed) timing chain would ultimately be a crank no start, with no compression on potentially several cylinders. In terms of stretch before a hard failure, you may have some misfires, lack of power, or excessive spark knock due to excessive timing variation. In earlier GM V8's, the cam gear had a nylon coating that would wear through on high mile engines, and oil change regiment had some dictating on when it would fail. I am not sure if yours has a nylon coated gear, that would be my only concern, in regards of replacing it due to time/miles. When the nylon coated gears finally gave up, all the nylon and aluminum from the failure, would go into the oil pan. In worst cases, that debris would clog the oil pump pickup screen if it was not removed. I can find no information that tells me your cam gear is nylon coated type. If you are of concern, the engine is not an interference type, so loss of timing does not mean valve damage.