I know this is 10 years later, but the thread helped me and I'm going to add to it.

Yes, it is one tab. It is on the outside (fender side) of the light. Do the Driver's side first so that you can see what you are doing.

Release the light fixture and bring it forward THEN unplug the bulb from the outside of the car. I replaced mine with a set of aftermarket clear lenses. The only issue is that the new bulb holders have a different pin pattern on them. I used the old ones in the new fixtures. No issues.

Plug the bulbs back in and hook them up to the wiring before you put the fixture back into the car.

Make sure you line up the two tabs on the inward side up with the two slots on the car then just slowly but firmly push the fixture into place. You will hear a clear click when the one locking tab engages.

I had to use a small flathead screw driver to push the rubber gasket fully into place. Again, no issues. They look good and work. Best of all it was $35 for a set of two fixtures, including shipping. (eBay)

Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.