Do I have to deal with a law firm that is pressuring me for an answer TODAY, regarding payment of deficiency balance of surrendered vehicle? They say they have been retained by the original loan company. Can I deal directly with the auto loan company eventho it has been a year ago we surrendered the auto?

No, it sounds like this collection agency bought the file from the auto loan company so you have to deal with them

There is no law that you have to deal with it or make a payment arrangement the same day they contact you, just eventually you will have to start making payments or offer them a partial settlement.

Collection agencies buy bad debts for a small percentage of the amount you actually owed so If you have the money handy I personally would suggest to offer them 50% of the amount they want and say you'll pay immediately. Get them to agree to it in writing (if you can) and be done with it!