Hi there Thorn,
Thanks for your info as I have the exact same problem. I need to replace the ballast for the D1S Xenon from the left (driver's side) and I want to avoid to pay for something I could do it on my own.
My first thought was if the headlight could be removed without removing the front bumper. The removal of the front bumper is kinda messy which would lead me to the mechanic.
My question is if you had to remove the wheel before removing the wheel arch to get access to the ballast.
I want to test some cheap ballasts I've found through the internet which means I might need to do that several times.
And if you have any opinion on D1S Led bulbs with canbus. Could LED versions of D1S, harm the ballast? Because I think my cheap D1S Xenon was the reason my ballast got damaged and now I want to try LED.