I actually replaced mine through the gap when removing the number plate light assembly, its do able if you've got the right tools and got small hands and wear thin cut proof gloves!, at the time I didnt want the bother of removing the inner panel but for ease of fitting probably should have..
I ordered mine cheaper through AliExpress, it came in a hologrammed box etc, and worked perfectly.
The only concerning thing I noticed when removing the old one was it was damaged from water corrosion, also signs of long term water ingress in the number plate lights, I'm not sure if this a design fault or the fact its a high miler (134K), and I'm not sure if theres supposed to be a seal there, I didnt notice one..