Lithuanian

I'm looking at a semester exchange to Lithuania. The courses I'm taking are in English but I'd like to get a grounding in the language before I go. Apart from Latvian what other languages does Lithuanian share origins with ? It seems completely different to all other languages within the region. I've studied a bit of Czech and found it not THAT difficult, but how does Lithuanian compare ? I hear it's a difficult language to master.

>>5
I'm Croatian, i don't speak Lithuanian but i found i was able to understand bits and pieces of speech in a documentary. Can't be that much different? both Slavic languages. Maybe it was just the similar words. 
On the other hand i learn Hungarian and Georgian. Both are hard as fuck