I usually post in the 210 column but am looking at 129's. What is the difference between a standard 2000 SL500 and the AMG version?
There was no 2000 SL500 AMG. However, (I am speaking for US specs models only), MB did offer sport package (called "AMG sport package") in 2000 for $5K which included front apron, rear bumpers, side skirts and 18 inch AMG staggered wheels.
There was another common package which included xenon headlights, CD changer, and heated seats but that's neither here nor there (nothing to do with sport package).
You can do a search. I am pretty sure that has been asked many times before. If you not sure, post pictures of the car here and I can tell if it has sport or not.