I ran into a similar issue with the key fob for my SHO. The SecuriLock Passive Anti-Theft System section of the owner's manual will tell you how to reprogram the integrated keyhead transmitter (IKT) & Intelligent Access Key.
The only replacement LED I've been able to find for the PH16W is this one sold by Diode Dynamics for the Camaro. Not sure if the $89.99 price is for a single bulb or set of two. Link below...