The problem is that I don't have the foggiest idea what is appropriate for a Catholic funeral that isn't a military funeral as well.
I'd say Catholic funerals probably reflect conservative cultural manners. The failsafe is to wear black, although if you were military, dress uniform would be acceptable.
Then again, there's also the family wishes. I've been to funerals where the request was to wear something celebratory, rather than mournful, 'we're here to celebrate the life of' kind of of thing ... but even then, I'd not go so far as to dust down my Mardi Gras outfit! Here it would be OK to ask if there's a dress code.
To make matters more confusing for me is that it's going to be held at one of the local cathedral, and I have no idea since I was raised Jewish. The only rule that I pretty much know is that my clothes have to be intact and not something that 'screams' "streetwalker".
That's about it, although I have also been to funerals where the black dress worn was something purchased for the office party. It's not a feckin fashion parade ... really it depends on how conservative/uptight the family is. The converse is I've known family members smile at a woman dressed in a stunning and seductive black outfit, from veil to high heels, and they all nodded approvingly — "He'll be smiling now," — not very PC, but it all rather depends on the family, I think.
+++
If it's at a cathedral, I'd assume it's going to be a grand affair.
If the body is not already at the cathedral, we wait outside until the deceased arrives. He's met by the priest, there's a sprinkling of Holy Water and reception prayers, then the coffin is conveyed to the aisle before the altar. The congregation file in afterwards.
There will probably be a Requiem Mass, much like the mass, but the readings will be related to the occasion, and usually by the family. Have some tissues handy. The priest might say a few words about the deceased, which I find dreadfully embarrassing when it's evident that he never knew the person. On the other hand, when my agnostic uncle died, the parish priest spoke highly of him, a man he knew and saw regularly, sitting at the back of the church while his wife was at Mass. He insisted that there would be rules bent on this occasion! He kept the balance of solemn/upbeat just right.
If there is a mass, then there'll be standing ups and kneeling downs and sittings in between, with prayings and maybe even singings ... hopefully there'll be an Order of Service with directions.
If there's communion probably best not to receive ... a lot of Catlicks get touchy about that bit.
After the Requiem Mass there's the committal. The coffin is taken to the cemetery and, OMG, THEY'RE STARTING ALL OVER AGAIN! Actually just a few short prayers, sprinkling of Holy Water, coffin is lowered, handfuls of earth/flowers are dropped ... that's it.
Then the reception.