Answer: First step is to run some basic soil tests and check fertility and pH. Based on the test results you will know how much fertilizer is needed and if you need to add lime, or not, and can begin to prepare the soil accordingly.
In the meantime, to preserve any existing lawn grass and cut down on weeds seeding themselves in the lawn, mow it correctly. This means set the mower high and mow often enough that you never remove more than one third the grass height at a time. In spring, this can mean mowing more than once a week.
The best time of year to do extensive lawn renovation work is late summer to early fall when the seed germinates and grows better, so you have some time to prepare.If the entire lawn really needs to be redone you would kill off the existing vegetation using an herbicide containing glyphosate per the label directions, then loosen the soil down about six inches using a tiller (which can be rented inexpensively rather than purchased) and work in organic matter such as compost, then level the area and rake it smooth, then seed or sod.
I would suggest you work with your local Penn State county extension to run the basic soil tests, evaluate the existing lawn condition, and plan what you are going to do. They can suggest the best grass varieties for your area and help you develop a maintenance plan.
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