That's exceptionally general. It's like saying you want to try food.
Consider the business section of the paper (can be online of course) to check on exchange rates. Those will start to give you an idea of costs. Go to travel websites (places like Orbitz) and see what their prices are. If they have links for things like ground transportation and accommodations, follow them.
Remember, any form of travel has the following expenses:
- Transportation to the site (for you, it'll be either plane or ship. Keep in mind, airlines charge fees for checked bags, and by definition you will have at least one checked bag)
- Ground transportation (would you rent a car, take public transportation, rent a bike or a motorcycle, try ride sharing, take taxis or buses? Even if you can walk long distances with ease, there will be times you're tired or have too much stuff to carry, or it's just plain too far)
- Accommodations (would you stay in a resort, a hotel, a bed and breakfast, a college dorm, a youth hostel, someone's house? Would you stay long enough where renting an apartment is cost-effective?)
- Food (will you cook, go to restaurants, try to get accommodations with meals included? Would you know where to shop for meals? Do you have dietary restrictions or preferences which would narrow your choices?)
- Souvenirs (this could be the trip of a lifetime so consider you will want to remember it with something beyond photos. Also take into account shipping if it's large, possible duties or taxes, wrapping things that are breakable, and if you have enough room in a suitcase or if you would have to buy one)
- Safety (do you need a safe in the room you're staying in? Do you need to limit your ground transportation choices because you're concerned about being robbed or assaulted? No one likes thinking about this stuff, but you should)
Also, consider how fit you are, if you can walk around a lot, if you must carry oxygen, etc. What languages do you speak or at least have a chance of understanding? People speak English in a lot of places, but that doesn't mean the street signs are in English.
How well do you roll with the punches? Do substandard or weird accommodations bother you, or do you shake them off as an adventure? How well do you adapt to how others do things? Are you going to get all bent out of shape if someone insults America or the president?
Think about the sights you would like to see. Museums? Old buildings? Natural wonders?
How long will you be there? That will define how far you can go from whatever your home base is. You can't, for example, see all of Italy in a week. You probably can't see all of Rome in a week.
Have fun-- much of Europe is lovely. But please, do some research.