Answer: My first suggestion is to mow the area as often as possible. You may need to hire someone with a heavy duty mower. Grasses are one of the few plants that can withstand repeated (weekly) mowing. By repeatedly cutting down the larger weeds, you'll deplete their root systems. Mowing, plus the boiling-water treatment for persistant weeds, should help you get a handle on things. (By the way, you can also try pouring white vinegar on the crowns, instead of boiling water. It's more expensive, but easier to handle.)
You might also consider a wildflower meadow of some sort, instead of sod. Once established, it will require less maintenance.
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