A discussion about "remote entry" and key fobs, inspired me to look further into this.
This may apply to most or all model years, but for my 2007 chassis, the owners manual has a procedure for the owner to program as many as 4 remote key fobs by themself. This is the procedure as described on page 60 in my manual. It also has a diagram illustrating the positions of the key.
How to reprogram your remote entry transmitters
You must have all remote entry transmitters (maximum of four)
available before beginning this procedure. If all remote entry transmitters
are not present during programming procedure, the ones missing during
programming will no longer operate the vehicle.
Note: Ensure the brake pedal is not
depressed during this sequence.
To reprogram the remote entry
transmitters:
1. Ensure the vehicle is
electronically unlocked.
2. Place the key in the ignition and
turn from the (2) LOCK position to
(3) OFF.
3. Cycle eight times rapidly (within 10 seconds) between the (3) OFF
position and (4) ON. Note: The eighth turn must end in the (4) ON
position.
4. The doors will lock, then unlock, to confirm that the programming
mode has been activated.
5. Within 20 seconds press any button on the remote entry transmitter.
Note: If more than 20 seconds have passed you will need to start the
procedure over again.
6. The doors will lock, then unlock, to confirm that this remote entry
transmitter has been programmed.
7. Repeat Steps 4 and 5 to program each additional remote entry
transmitter (up to four transmitters).
8. Turn the ignition to the (3) OFF position after you have finished
programming all of the remote entry transmitters.
9. The doors will lock, then unlock, to confirm that the programming
mode has been exited
In another discussion, someone stated they are missing the electronic receiver in their vehicle so if you too lack that receiver, you would have to buy one.
I'll have to buy some fobs and try this myself. Doing some quick shopping on Ebay, it seems I can buy 4 new fobs for $70 total, including shipping. I have made contact with a new fob seller, and will report back to you on my findings. $70 for 4 new fobs seems too good to be true.