We have an off site septic system. The 2" pvc service line is 964 feet long; we think it has been ruptured. How do we locate the line, and identify the area that needs to be fixed?

Not sure where you are but that line should not been put in with 2" pvc. Way too small, especially for nearly 1000 '. SeeSnake and GenEye have digital locators that can reach up to 400'. You next to do some searching for a sewer company who has one but they are so expensive, $10k, it will be difficult to track one down. A cheaper method would be to hang dig a tets hole every 50' or so. Most septic lines are only about 2-3' down. Start with a straight line between the house exit and the tank. There should be few bends but with 1000' who knows. I'd replace the whole run with 4" but you are talking big dollars for that unless you can trench yourself.