stereo problems-volume-radio

This problem has occured for years, I turn the volume up and the sound either goes off fades away or gets louder, its opposite sometimes and somtimes it just doesnt work at all, does anyone else have this problem? Next, how do I remove the door panel without messing up the plastic frame, also how hard is it to replace the speakers and stereo myself ive heard the wiring is tricky. also could this just be a volume knob problem? I told the dealershp about this before years ago when it did it less (its a 99) and they said its just "tounchy" there were full of ____. Anyway its gotten worse no as im driving around for 15-20 with no music and i have to keep messing with the knob to get it to work-thanks