Actually, not that difficult a job as I found out a few weeks ago! Had the same issue and this article by
Mr CL7 helped me get my headlight unit out of the car.
The only hiccup I had was the 10mm socket wrench where the extension wasn't long enough. Recommend you have at least a 4 inch extension. 6 or more will make it a cake walk!
Once out, take off the plastic caps, remove all the bulbs and then use a hair dryer to clear up the moisture. When cool, then replace the bulbs and re-seal.
If the problem returns it'll be the sealant & clips that have gone. You'll need to either replace it or pry the unit apart and re-apply new sealant. Let me know if you need help with that as I had to do that too.