The best thing you can do is to prepare your soil so that whether you use seed or sod, the grass will get off to a good start. Till in a good portion of compost or peat. Make the soil reasonably loose and friable. You should have no trouble turning it with a hand shovel.

There is not much you can do about the weed seeds. What you are trying to do is to get the grass to compete well with the weeds. When you are able to start mowing the grass, that will do a great deal to help the grass compete with the weeds as well. When the grass is growing well you will be able to use a herbicide such as Weed-be-Gone without fear of damaging the grass.

You will have weeds in your lawn. Some from the seeds already in the soil and some from those that are blown or brought into the lawn. A healthy turf, mowed to the right height will go a long way towards keeping the weeds to a minimum.

Be patient. Even if you sod, it will take a couple years at least for the lawn to knit together and start looking the way you want.