303 will help clear up some of the micro scratches and make it look a lot better. I've used it for 10 tears now on my sun faded top and rear window and most think my top is only a few years old. I thought that was one of the first things I was going to have to do to the car when I bought it. (or just keep the top down!) But 303 gave it new life even if some of the seams are coming undone...
As others have said you really can't polish the soft material of the window. IF, you do try, try a very small area under the top flap if possible where it won't show. But any type of polish will be adding scratches and heat which may also warp the window in additions to the swirl scratches...
Try the 303, you may be surprised at how much it may help as is. And if you replace the top or just the window, you'll be able to protect it for years to come with the 303 you buy.