Looks like it's a 1998, based on the catalogs at vintage-trek. At first the Buenos Aires was 853, then became 525 or a mix of the two. The 1998 page says it was pearl light blue w/royal yellow panels, so that matches.
Not sure re: the size, although I see a 57 on the BB, and visually based on the headtube that seems about right. It might be a bit tall for me. I have ridden from 54 to 58, and I know people say these are long, but I have also seen people say it's not that simple.