As a precautionary measure, i'd suggest draining the water from the fuel filter (should be a tap of some sort on the bottom of the filter) and adding a fuel system/injector cleaner to a full tank of fuel before you set off. Also carry a spare can of fuel, just in case you find yourself in the middle of nowhere running low on fuel!
If the car has covered 170000km since new, that's about 100000 miles, a figure most D6 owners would consider just about run in so i wouldn't envisage any problems.
As mentioned by others, take a few of the "obvious" spares with you such as belts, fuel etc and give the car a general check over. I'm guessing it recently had an oil/filter change from everything you say but i'd certainly change the oil/filter on your return. I believe the interval for cars of your age was 3000miles/5000km for oil/filter changes, you'll be doing 2000km so would be wise to change the oil after as it would be approaching the 5000km figure assuming the previous owner and you have both used it since the last oil/filter change.
Other than that, enjoy your road trip!
*** EDIT *** Just noticed you said 200km and NOT 2000km - might make some of my comments seem a bit over the top!
