Definitely the drivers side (if your car is RHD) the arch liner is held in by a few screws, I tried to do mine from underneath on axle stands, tbh the 'through the arch method' is much easier. Iirc it is 3 x 5mm allen key bolts, just remove the connector plug undo the bolts and off it comes. My mechanic did mine in the end during other work so not sure about locite, can see that is necessary though.