S3 8L Replace door speaker Bose

First lower the window, then remove the 2 visible screws at the top on either end of the door card, remove the single screw inside the grab handle, push down the plastic cuff inside the grab handle and remove the 2 main screws behind it. Pull the whole door card straight up and out, but not too far as you need to unhinge the door release cable and unplug the wiring looms.
Bose front speakers for an 8L are pretty rare on ebay but they do come up. Are you sure it's the speaker and not the amp, as the amp is more prone to failure, usually a dry solder joint on the PCB. If the tweeter still works OK then it's the speaker, but if the tweeter crackles as well then it's the amp as they both run off the same channel & wiring.