I cant tell which part is messed up (I hit it with a hammer accidentally while trying to get my tire off). Do I need to replace the whole system, or just the body?
Yes, you need to have the whole thing replaced. That appears to be a stem for a tire pressure sensor. In order to fix this, you'll have to have the tire broke down, then pull the sensor off the rim. Then disassemble the sensor and place the guts into a new shell. You could just put in a new sensor, but you'd then have to have it programmed into the tire monitor system.