Replacement Xenon Headlight - Failed DRL

Ahoy there.

I have a 66 place VRS pre-facelift with the cornering xenon lights.

I got an alert on the dash about needing to check my drivers daytime running light back in January when it was particularly cold and wet.

I checked the engine bay and somehow, the rear cover on my drivers side headlamp popped off and water had gotten in. The cover was sitting there in the engine bay, I tried to dry it out but with the freezing weather I was unsuccessful and the DRL has failed so it alerts everyday now.

Am I right in assuming I need to replace the complete unit? Nothing about the unit looks user servicable.

Am I right in assuming it's a bumper off job?

I'm going to get a 2nd hand part, (these things aren't cheap!) can I get any adaptive Xenon unit from the pre-facelift 2013-2016 era and it'll work?

Has anybody done this job? I assume I'll need to pop my existing bulbs and control modules on the unit.

Any other jobs you'd recommend doing while the bumper is off?

Thanks for any help!