Re: cleaning front door speaker plastic grill
Most cars today have a one-piece door panel that contains the speaker grill, and the speaker itself is anchored to the steel innner door skin. On some cars, you must remove snap-on access panels and several screws before removing the door panel. And, often, there are plastic clips holding the door panel in place that will likely break when you remove the panel. They can run $2-3 for each clip, and there may be as many as 5-7 clips holding the door panel in place.
As for cleaning the grill, try using some Q-tips soaked in a mild cleaner such as Simple Green on the grill openings to see if you can get far enough into the openings to remove the stain.