not 'massive' but again not a 5 min job. bumper off, both headlights removed. Then fit new xenon headlights from full fat 172/182. The light loom may need altering somewhat as i'm none too sure on the loading of the ballast/ignitor units. But providing everything is ok on that side of things I can't think of any other issues...?
The auoto levelling and washers are only a legal requirement if xenons are fitted in the factory, which of course yours wont be so they aren't an issue unless you want them to be.