Answer: Any existing vegetation should be removed, to do that you can use an herbicide containing glyphosate. Read and follow all of the label directions. The soil should be loosened down at least six inches and you should work in several inches of organic matter such as good quality compost. Also add starter fertilizer and limestone as indicated by the soil tests, working them into the top six inches of soil. (The 6.0 you mentioned is adequate for lawn grass so you would not have to lime now, but you may need to spread some lime in a year or two as pH drifts over time.) In some clay soils it can also be helpful to add coarse sand. Please consult with your local county extension for help in determining what would be optimum with your local soil type. In the meantime you may also find their web site helpful.
Good luck with your lawn!
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