My girlfreind just bought a used 09 300 and only got one key with it, if I get another key and fob from other then the dealer "do I have to" take it to the dealer to get it to work on her car or can I program it myself? The fob comes with a blank key already just needs to be programmed to the car. Thanks

 

yes U will need to have a dealer program it

 

If you have one working fob, you can program another. Actually, you will have to program both the new and the old at the same time (one immediately after the other). If your car has a security key, you will need two working keys to be able to program a new key without going to the dealer.
The routine for programming the keys and fobs is set out in the owners manual. (Get one at Chrysler.com)
If you have only one security key, you will have to get the dealer to program another one for you. It will be more money than you want to pay for it, but you really should have more than one set of keys.
Next time you buy a used car, demand that they supply two sets of keys.