Apparently I didn't do my homework well enough when I went to an opera there. My seats were really bad, even though not so far back in the theater. My advice is to orient yourselves as nearly square with the stage as possible, and not worry so much about being close. As someone else pointed out, you can click on the empty seat to see the view from there; it's a little prone to glitches, but keep clicking till you get it to work. But envision what the view will be like if parts of the opera occur far back from the front of the stage; just because you have a good view of the front of the stage from the side box doesn't mean you would be able to see all the action.
Yes I would agree that if you are in a side box you want to be in the front row (although I must say that the two people in the front row of my box couldn't really see either, at least not without standing up to lean out of the box and crane their necks to try to see where some of the action was taking place). But if I had it to do over again, I would go for the rear of the theatre with a good straight-on view of the action.
In spite of my experience with seeing, I had a wonderful time there, just soaking up the ambiance and listening to the divine music. So definitely go.