I'll have to defer to someone more current on the study abroad question but I believe the opportunities to do so while at USNA are very limited, if they exist at all. There are various opportuntities to study abroad after graduation as Fulbright scholars, etc. Your summers are filled with training and, other than a possible exchange to some other military school, I'm not sure you could complete your major requirements at a civilian school.
In the past, there have been opportunities for a very few mids to spend their first class summer with a foreign navy (replacing the summer cruise with the USN) as an exchange student. But it's not classwork and I don't know if that program will continue under the current administration.
In terms of language while an engineering major, I believe you can do so under two circumstances. First, if you validate your first two years of a language, you can take the more advanced language classes to fulfill your humanities distribution requirement. Second, if you validate sufficient courses to free up your schedule, you can take whatever classes you like to fill your day. Thus, it's hard but not impossible.
As for info on the Systems Engineering major, you should check out usna.edu under "Academics." Lots of information there. Are there specific questions you have that aren't addressed there?