I noticed what i think is my heat shield hanging off under the rear of the car near the muffler is this something i need to replace immediatly
It would be wise, just take it to an independent muffler shop. They could probably reattach the shield.
It protects the rear interior of the car from becoming too hot. It may also protect EVAP, brake lines and wiring from heat. Many times by removing the screws that hold it up and putting washers on them, you can salvage the old shield. It should also be short order for a service center.