Jim - for the pre-03s you can add new keys yourself but you cannot add new remote FOBs. I am assuming he is talking about a pre-03 since he is asking about adding a keypad - the pre-03 didn't come with them.
Here what my 01 manual says:
To add another remote FOB:
Replacing lost transmitters
If a remote transmitter has been lost and you would like to remove it from the vehicle’s memory or you would like to purchase additional transmitters for your vehicle (up to four may be programmed into memory), take all your vehicle’s transmitters to your dealer for programming. It will be necessary for your dealer to reprogram all the remote transmitters to your vehicle while performing this service.
To add another key:
spare keys
A maximum of eight keys can be coded to your vehicle. Only SecuriLocky keys can be used. To program a coded key yourself, you will need two previously programmed coded keys (keys that already operate your vehicle’s engine) and the new unprogrammed key(s) readily accessible for timely implementation of each step in the procedure.
If two previously programmed coded keys are not available (one or both of your original keys were lost or stolen), you must bring your vehicle to your dealership to have the spare coded key(s) programmed.
Please read and understand the entire procedure before you begin.
1. Insert the first previously programmed coded key into the ignition and turn the ignition from 1 (LOCK) to 4 (RUN) (maintain ignition in 4 (RUN) for at least one second).
2. Turn ignition to 1 (LOCK) and remove the first coded key from the ignition.
3. Within ten seconds of turning the ignition to 1 (LOCK), insert the second previously programmed coded key into the ignition and turn the ignition from 1 (LOCK) to 4 (RUN) (maintain ignition in 4 (RUN) for at least one second but no more than ten seconds).
4. Turn the ignition to 1 (LOCK) and remove the second coded key from the ignition.
5. Within 20 seconds of turning the ignition to 1 (LOCK), insert the new unprogrammed key (new key/valet key) into the ignition and turn the ignition from 1 (LOCK) to 4 (RUN) (maintain ignition in 4 (RUN) for at least one second). This step will program your new key to a coded key.
6. To program additional new unprogrammed key(s), repeat this procedure from step 1.
If successful, the new coded key(s) will start the vehicle’s engine and the theft indicator will illuminate for three seconds and then go out.
If not successful, the new coded key(s) will not start the vehicle’s engine and the theft indicator will flash on and off. If failure repeats, bring your vehicle to your dealership to have the new spare key(s) programmed.
In 03 they added the procedure to add DIY FOBs:
How to reprogram your remote entry transmitters
You must have all remote entry transmitters (maximum of four) available before beginning this procedure.
To reprogram the remote entry transmitters:
1. Ensure the vehicle is electronically unlocked.
2. Put the key in the ignition.
3. Turn the key from the 2 (OFF) position to 4 (RUN).
4. Cycle, eight times, rapidly (within 10 seconds) between the 2 (OFF) position and 4 (RUN). Note: The eighth turn must end in the 4 (RUN) position.
5. The doors will lock, then unlock, to confirm that the programming mode has been activated.
6. 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.
7. The doors will lock, then unlock, to confirmthat this remote entry transmitter has been programmed.
8. Repeat Step 6 to program each additional remote entry transmitter.
9. Turn the ignition to the 2 (OFF) position after you have finished programming all of the remote entry transmitters.
10. The doors will lock, then unlock, to confirm that the programming
