First thing I'd do is have a camera inspection of the whole line. You want to make sure how much needs to be replace or if a less drastic repair would be enough. Replacing sewer line is not a job I would recommend for DIY. Sewers are usually quite deep so there is a real danger of cave-in not to mention the shear amount of digging involved which, even in ideal soil and conditions, can be exhausting. Then there is the need to keep the proper slope in the new line. If the line settles after it is covered, you're almost back to square one. I'm like you, more time than money, but I've got a few years head start on you, and I'm finally learning that my mind can conjure up jobs that my body can't cash.