Hi.. I'm getting married there. Don't be nervous.. But I would like to just tell you is that they are a little strict on their rules day of the wedding (ie: can't have an aisle runner, or flower petals AT ALL, only thing you can use after is bubbles, and don't hold me to it, but I think you can't specify or bring your own alter flowers. And then there are some rules the photographer and limo guys have to abide by as well).. So.. annoying rules, but I've always wanted to get married there, so I am dealing..
To answer your questions, Even to the office, I personally have an issue with people wearing jeans or sweat pants to church (both of which I even saw people wear to a wedding recently ).. so I'd say casual, but not jeans & flip flops or sneakers. When I went we each had to fill out a questionnaire privately with the priest, while the other waited in the other room. Don't really remember what they asked so couldn't have been that bad! They do ask about if you were both baptized and confirmed and where. They may ask if you live together.. Assuming you are both catholic and confirmed, I don't think they would tell you no unless your date is already booked. FM if anymore questions..