Answer: It won't be easy, but you can start a healthy new lawn by completely removing the old lawn with a rototill (which you can rent). After rototilling the area, rake to remove all the old grass and roots, along with any large stones you unearth. Roughly level the area and spread some organic matter over the top, then rototill again. Level the area to be planted (allow a slight slope for rainwater runoff - directed away from any buildings). Once the area has been leveled, broadcast your seed (or lay your sod) and water as necessary to keep the seedbed moistened. Grass seed generally germinates in 7-10 days.
Best wishes with your new lawn!
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