Travelling to Uruguay, you need valid passport only, when travelling by car, the international driving licence and valid documents, regarding the vehicles, are required.
The citizens of European Union do not need the entry visa for tourist stay, not exceeding 90 days. So called announcing duty is not introduced in Uruguay, the foreigners are obliged to fill in the entry/leaving forms at crossborder.
The airport tax in a moment of departure from Uruguay, to final destination in Argentina, makes USD 17, and to the other destination (with a change in Argentina) it makes USD 31. The holders of diplomatic passport are not obliged to pay airport tax.
Information and warnings on travelling abroad is to be found HERE.