Sheesh, talking about thread necromancing.
Well, one thing I know for sure is there's one Amiga store in Germany:
http://www.vesalia.de (they can speak English afaik)
Considering your problems with your A4000, buy contact spray and compressed air from any electronic parts shop, spray every connector with it and blow clean it with the compressed air, take socketed chips out and spray clean them as well. Check battery and if that has leaked, clean it with some lightly soggy cloth and replace the battery (though chances are it has destroyed your Amiga). If the battery hasn't leaked, yet it still doesn't work, you could (let someone) replace the capacitors.
Oh, btw. don't worry about the contact spray, it doesn't short anything at all.
