Answer: Starting a lawn from sod requires thorough soil preparation, then once the sod is laid you must keep it evenly moist until it becomes rooted and established. You need to know the measurements of the area (length by width in feet) to be covered, from that your supplier can tell you how much sod you would need.
Here are instructions on how to measure your yard. (You may need to cut and paste the complete url into your browser to make it work correctly.)
Here is some information about lawn care and starting new lawns. It is geared toward Maryland however it should also apply to DC.
specific instructions for sod
There are many perennials that grow well in the Washington DC area. Some of the best for a sunny location might include purple coneflower (Echinacea purpurea), black eyed Susan (Rudbeckia fulgida), Baptisia, Coreopsis, daylily (Hemerocallis) and sedums. For a shaded area you might try an assortment of hostas and ferns along with Hellebores.
For general landscaping and design tips for your yard, you might want to look at a book or two about landscaping. The Dummies series includes several that would be helpful to you -- including landscaping, lawn care, house plant care, and perennials. They are widely available at libraries and bookstores. Another inspiration can be magazine photos. For detailed help, you might want to bring in a garden designer to consult on an hourly basis (be prepared with questions and take notes) or to draw up a custom design for you.
Unfortunately, with so many questions at once it is difficult to give you complete answers. If you would like to follow up, please do so -- but please put just one question or topic per Q&A form so we can give you more thorough information for each. But I hope this helps you get started.
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