You'll be much happier if you replace the clay pipes with ABS pipes. That will keep the roots from coming through again. Use nitrile gloves to keep the black gunk from the clay pipes off of your hands. I've done this and agree that it is definitely a dirt job. Don't worry about saving the old pipe. If you have access to a jackhammer or trencher to dig the trench, feel free to use it. Copper sulfate can be used to slow the invasion of roots back into any leech field.