Aerate if you can. Throw down seed. Throw on a late fall/winterguard type fertilizer. This will give you solid good growth next Spring. This won't solve your weed problem, but it'll get your grass back in the game.

Next year you can attack the crabgrass and weeds with a pre-emergent like a Scotts Step 1 or any other weed and feed type product.

This is the least amount of work you can do with decent results to fight the weeds next year.