It's natural to worry about about new and different things when you're taking a step to do something completely new.
Hotels in Europe are required by law to collect your passport information when you check in and Americans are famous for making this more of a big deal than it needs to be. Some people also really worry and puzzle over taking trains and buses and want to default to renting a car - which is expensive and troublesome - when they don't need one.
I always remind people that as exotic as these places feel when we visit as tourists these are just cities full of people who are living their everyday lives. They take trains and buses to and from jobs, friends, school, etc everyday and we're just visiting their hometown for a few days. Everyone here works, shops, cooks, goes out with friends just like we do so don't worry so much about stores, transportation or daily needs and just assume you'll be able to sort things out if and when you need to.
I do use a money belt and pants with an internal zippered pocket to keep passports and credit cars safe - even in places where it seems silly - to put my worries to rest and just relax about everything else and try to fit into everyday life as much as possible.
I'm a planner so I'd say plan and learn as much as you feel you need to beforehand and then just go and enjoy it. Things will go wrong, you'll mess something up but all of that is fine and virtually everything is fixable. And hopefully for everything that goes wrong there will be unpredictable things that will go your way as well and provide memorable experiences. As Ricks says just travel in a state of eternal optimism and enjoy all the aspects of the experience.
Have a great trip,
=Tod