Stamp a new blank 2003pontiac grand am key?

Not sure what you mean by "stamped," but the cost to have a key cut is nominal - a few bucks (assuming you have a key to copy from). If you need a transponder key, the blanks cost a lot more, the cost to cut it is the same, however the car needs to be programmed to accept it. Your owner's manual will have the procedure for that. If however you have NO key now, you'll need to have this done at the dealership and costs will be significantly higher. Some dealerships maintain a key code record and can cut a key from those, but that may not be available for your car. Most locksmith shops can cut a key, I even had one make a key from impressioning, but all the costs are in getting a chipped key programmed to the car.

if u saved the build code for the key..70$ and it came with the car. on each key was a code tag with the key.