At university level in Ireland, the primary focus of the course is not really the language, but the literature. This is not to say that learning the language is not essential, only that people often go into these courses and later realize that it's in actuality a literature course as much, if not more, than a language one.
With regards to the literature, you'll probably read translations in the first year anyway and literature exams will be answered through English.
I'd imagine that you'll likely cover 'i promessi sposi', Dante (or at least l'Inferno), Piranedello and no doubt some pet writer that the departmental Professor specializes in that no one's heard of in Italy.
You'll also cover other modules along the way, in many cases optional, such as Italian history, socio-linguistics and possibly even opera or film.
Nonetheless, you will be taught the language and by the end of your degree you should be reasonably fluent or at least have a very good working knowledge of the language. It would be advisable, however, to consider spending time in Italy too, possibly applying for ERASMUS, to better improve your language.
But is it wise to begin a language? Sure, there's no reason why you cannot do so, especially when you're still young; I learned new languages much later than that.