Sound like you may have some major problems. I think you're wise to get it properly inspected and evaluated. Often sewer lines are quite deep and it's really not a job you should try to do yourself. When you get to the depth where sewer lines often are, beside a huge job of hand digging, you run a real risk of having the trench cave in on you. Hiring cheap labor isn't too good an idea either since you would be liable of any injuries incurred.