I feel your pain man--when I bought my 99 it had a big stain on the passenger door from gas. I didn't notice it when I bought the car and was really upset when I saw it in the sunlight one day... I had good luck using good ol Windex and scrubbing it really good a few times. Then I just waxed over the area and you would never know it was there!
I thought Windex has some harsh chemicals in it that would ruin the paint and finish on a car. And I thought that Windex can only be used on windows and chrome.