You are referring to the sensor in the front bumper correct? I've never replaced one unless the mounting bracket is bent. These sensors do "reset" on their own. Think about it, if it didn't reset itself, the new air bag would go off as soon as you plugged it in and hooked the batt back up. That wouldn't be a smart design, lol. But if you want to replace it for peace of mind, no harm done. See ya, Will
What I did is I purchase airbag simulators to take the place of the airbags (from Helms)for abour $50 shipped. Once you start the car if the system has a problem with the crash sensors it will give you a code by flashing the air bag lights. If not then you should be ok. This way you don't risk the loss of expensive airbags or worse body parts.