You can sod the other half acre the builder doesn't yourself if you really want an acre of uniform grass.

Grass is about the easiest thing to grow and you are in the right season.

Whether the seeded grass will match the sod is another story - but find out what the sod is and match the seed. In my area, and in this time of year - planting a lawn is easy - kill all the weeds, get some topsoil, rototill it lightly, pick out the weeds, sticks, etc, seed and water. You'll be good to go.

In northern Virginia, you will be happiest long term if you plant zoysia plugs. It's more expensive short term but the long term results will pay off.