You also need to make sure it uses the US frequencies if you plan on using it here in the US. I know the 8707 is only GPRS capable in the US. Almost useless.
GPS should work no matter where you are as it is a worldwide network. The issue could be map coverage to get useful information, but I think BBMaps and GoogleMaps work in Europe.
Also check out the FAQ before buying a used BB. It is much different than buying a used cell phone. Will save you some headaches later on. Buying a BlackBerry off eBay - BlackBerryFAQ.com