Re: Travel to Europe...
I've been to Europe about a dozen times over the last three/four years for business/leisure and both. There is a lot to see/do and even in 2-3 weeks you won't get to everything.
First thing: season. Go for spring and not summer. Not only does it get hot as hell in the summer, Europe is overrun by tourists. Getting up the Eiffel Tower or into the Louvre can be a battle. The Colloseum in Rome is handling huge queues to get in. They don't show you that in the brochures, so be prepared.
We did a lot in winter actually. The weather stinks, but there are few(er) people.
A cruise may not be a bad idea cost and logistics-wise, but you will spend a decent amount of time on the boat and the shore-trips could leave you wanting for more. For example, they may take you to Rome or Florence for a day. It's not enough. However, this being your first time, it is more structured and could be more comfortable for you.
And there isn't that much sail time between ports. But if you've cruised before, you know the boarding/de-boarding can be a hassle. (At least it is in the Caribbean).
Since you do have time to plan, look into arriving in one country and leaving from another. You may fly into Rome, for example, and make your way by train to Paris and London and fly back from there. (Rome-Florence-Venice-Milan-Marseille-Paris-London or something like that).
I've never done Europass, since we usually did shorter one or two country trips. For a long trip with a lot of rail, its probably worth it.
The Euro just dropped under 1.20, which is good for you. But stuff is still going to be expensive. Good Luck.