Don't really know the answer to your first question.
I know it is vert hard to remove the grills from the stock plastic cups. I tried a blow drier (didn't heat up enough), but the glue seemed to be different (stronger) than the glue that holds the driver into the cup. I also tried boiling them in hot water, but this warped the cup. You may have too break the grills to get them out, assuming you are replacing them with something else (metal screen maybe).
Yeah, I figured so. Thanks.