I recently purchased a used 98 Sentra GXE, with a 1.6L dual overhead cam, 16 valve engine that was making some timing chain noise. The local shop looked at it and determined that the upper chain is loose, the upper tensioner has failed, and the chain sprocket is missing some teeth. They didn't think it was worth rebuilding. What do you experts think? I know some shops are reluctant to step into jobs like this, but I am not really excited about trying to drop another wrecking yard engine in. Thanks for your input in advance.