Ignition lock cylinder

Hi. I have had an issue with my anti-theft system from a few years ago. The solution that I used, with the help of a mechanic-friend of mine, was to bypass the system. It worked until a few weeks ago, when I used a new mechanic for a few different, unrelated repairs. A few weeks after receiving the vehicle back, the car would not start. After a few hours of checking other possibilities, I decided to try the eleven minutes on, thirty seconds off key reprogramming fix. Thankfully the vehicle started! I figured I would buy a new ignition lock cylinder and fix the problem once and for all. RockAuto had an AC Delco one for less than $100.00, which I bought. But not after viewing the following four minute YouTube video showing how easy it is to install. The problem is that the cylinder needs to be assembled and has very small springs and a bunch of other tiny parts that would be more commonly found on the workbench of a jeweler! Not only that, the instructions are asking for the code of the key. I do not have a code! I bought this car new fifteen years ago. It came with two keys and two key "fobs" for opening the doors and trunk remotely. On the key fob, there are three lines of information, with numbers: First line is GM/Lear with some numbers, second line is FCC ID information and the third line says Canada with some numbers. Do I need to use one of the numbers on the fob? This ACDelco cylinder did not include keys, rather it said, when I bought it, the existing keys could be reprogrammed. Looking at some other brands on RockAuto, I see that some do come with new keys. My new mechanic, who will install it for me, after first putting it together(!), first needs the key code. Where is that located?

https://www.youtube.com/watch?v=l7f0W06Jr_Q

https://www.rockauto.com/en/moreinfo.php?pk=948286&cc=1410466&jsn=8&jsn=8