If you use a mix containing mostly perennial ryegrass, you still have some time. This will germinate whenever the temperature is over 32 degrees F., but takes longer (up to three weeks or more in cold weather) than it would if planted sooner. If your mix contains Kentucky Bluegrass and/or fescue, these will not germinate well, and you will have to sow thickly.
Make sure the soil is moist, and that the top inch or so (not too deep) is worked to a fine tilth. Rake the seed in lightly, don't let the seed go very deep, as this causes much of it to rot before germinating in cold weather.
As for weeds, you really have to take care of them as they appear, as obviously you don't want to apply a pre-emergent to newly sown grass seed. After the grass is up, but before it freezes, you may be able to get in a treatment, but I think you'll have better results in spring. Don't try to control weeds right before winter if large amounts of precipitation are expected. If your grass germinates long enough before the ground begins to freeze, and you see some broadleaved weeds coming up, you can apply a general broadleaf control such as clopyralid, dicamba, 2,4-D, mecoprop, quinclorac, etc, or a three-way. It's possible that some of these aren't available to residential people.
But again, control will be better if you wait until spring, and the grass will be more ready to fill in and cover the soil, which will help inhibit further weed development.