I'm guessing you can get a 12-to-230 unit in your home country, but of course I've never shopped for something like that.
How easy/hard it is to wire up the external power control really depends on the laptop. I tried and failed with an IBM T41, so I bought an HP 530 because someone said it was easy, and it was in fact pretty easy. Unless you can find a post from someone who has tried it with your laptop, you'll just have to find out for yourself.
What's hardest depends on where your skills are. I figured that molding the screen into my dash would be hard, so I paid someone else to do it. Everything else was fairly simple it just took time and effort.
Someone else with an Audi 100 will have to answer the screen question, I have no idea.