Check rules for what you need to carry in the car too. I think some countries you have to have a triangle and, um, a torch (or something like that)
It should be fun. A European road trip is a great thing to do.
Last year i did the Ramshackle Rally (in a £200 Nova SR) to Krakow, Poland. It took 4 days and was a great laugh. This year we are doing the trip to Split in Croatia.
Im sure you will have great fun on those European roads - especially in a 172!!