My old WS.6 had the driver side headlight gear strip. Does the lamp go up, then down immediatly after you lock/unlock the car, then make a horrible grinding sound for about 5 seconds? If so, headlamp gear.
Luckily, mine was still under warranty, so I didn't dick with it. I just let the dealership fix it. They replaced the whole motor assembly itself, and I think they said that was over $300 itself!!!
But, like Joe said, it's an easy fix. You can either:
1. pull apart your motor assembly and flip the cheapass plastic gear and wait for it to strip that side, or...
2. buy an aftermarket brass gear that won't strip and only replace it once for the life of the car.
I've been out of the F-body circle for about a year now, so I can't really point you where to find the brass gear, or a write-up on how to fix it. If I were you, I'd do a search over on LS1Tech.com for more info. Hope this helps.