I need a replacement sensor for # 1 sensor of 670 system. Will this work??? Does it need to get reprogrammed ? If so, how does this happen?

Yes, this item is for replacement of your sensor. Numbers on the sensors are for refrence only. they are handy when you just get the system and helps to installed the sensors accourding to the defualt settings. Once you receive a new sensor, you will need to pair to your head unit. If you wish I can send you a manual to show how to pair as well.