I can't give you details for your own boat, but I've chartered on the Rhine recently. The skipper will need an ICC, but as long as the skipper is aboard, anyone else can drive.
One important point is that if you wear glasses, you'll be expected to have a spare pair, in case anything happens to your main ones.
As to kill cords, I was told off for connecting the one on my charter boat to my leg, as the owner said it would make the engine stop if I moved away from the helm. I tried to reason that this was the exact purpose of kill cords, but he was adamant that I keep it wrapped around the throttles! :O
Watch out for the commercial traffic - in Germany, they're known to simply drive over anything in their way, with no care to colregs!
Hope that helps!