Check your garage door opener mfg, most are rolling code these days... Follow the instructions in the homelink website given above and it's easy peasy once you understand what the different homelink blinking and solid lights mean. I just did mine last week, once you have the sequence down it takes all of 2 min (less if you can climb a ladder really fast or are tall enough to reach the learn button on the drive unit). Just remember that the car must be on (not necessarily running just the electricals need to be powered).
There's no need to panic until it is time to panic.