A detailed program will be provided with when to stand, when to sit and when to kneel. When to sing and what the lyrics are as well as the readings that will be read during the ceremony.
Yes, there is a dress code or at the very least some guidelines as to proper attire for attending a Mass. Holy Apostles recommend modest dress — meaning avoid bare shoulders, shorts, flip flops, mini skirts, athleisure and exercise wear, bare midriffs, lowcut or revealing tops, ripped pants, ball caps, etc.
If you have never been to a Catholic Wedding and would like some more information here is a video provided by the United States Conference of Catholic Bishops. Skip to minute 6:50 for the Rite of Marriage https://www.youtube.com/watch?v=M6yxxbWMKzk&t=14s
Here is a short video that discusses five differences of a Catholic wedding versus other Christian traditions. https://youtu.be/lgM3Bit-TZU?si=AuvCRoERbLf6wRU_