so your old one will still work as long as they don't pick that particular slot.
usually if you are replacing a key or fob that was lost, the dealer will ask you to bring all the keys or fobs, then they erase them all and reprogram the ones you have.
I need to pick up a new fob. I have a 04 v6. Will go by the dealer tomorrow to see if it's outrageous. If it is will get one from fleabay and try to program it myself. Thanks