Destination Wedding- Europe

I want to have a destination wedding in Europe somewhere. In a big cathedral or castle. But I really dont know where to start. Im affraid of getting ripped off since Im so far away. Im in California. I thought it would also be cheaper than having my wedding here, or at the very least ill get the most for my money. I plan on only having about 20 people at the most and thought i could get married during the week to save money. If anyone has been in this situation or anything please give me some advice on what I should do or if you know about the costs. I want to end up spending under $10,000 for everything. Some of my guests want to help by paying for their own plane tickets.
Thanks!!