Drivers side front door panel speaker not working

I noticed today that the speaker on the drivers side front door (down around where your calf is) isn't working. I've only bought this car about 3 months back 2nd hand from the dealership, im unsure if it was ever working >.<

Wondering how to gain access to the wiring behind it (removing the panel? And how to put that panel back in.) So I can first check to see if it's just a cable that has come lose, or if the speaker itself is dead - replace it myself with another of the same type bought cheaply rather than being charged out the nose at the dealership for it's repair.