I am not sure what you mean by a blessing. If you mean you are simply commemorating your original vows and receiving a blessing on your current valid marriage, you will probably be called up after the homily, or after communion, introduced, receive the blessing, be congratulated by the congregation and that’s it.
If you mean your civil marriage is now being convalidated, that is, you are exchanging vows with the priest or deacon as the official witness of the Church so that your marriage becomes valid in the eyes of the Church, you are from the Church’s point of view being married for the first time. There is a lot more to it. At least in this state you need another license, two witnesses, and some preparation (here it is attendance at a Convalidation Conference with other couples and presenters who explain and teach the meaning of Christian marriage).
The exchange of vows is the same as in any Catholic celebration of the sacrament of marriage. It can be done during a special Mass, during any Sunday or daily scheduled Mass, or before or after Mass, or outside Mass in the Church or chapel. If outside Mass, it can include a Liturgy of the Word (readings, usually related to Church teaching on marriage) and may or may not include a communion service. If many or most guests will not be CAtholic, a communion service is not a good idea.
If you are having an elaborate ceremony you and your attendant may wear whatever you want, even a wedding dress. If it is a simpler quiet ceremony, whatever clothes are especially appropriate for Church --dress or suit for women, suit for men. Modesty is the key word to remember here (you may have to remind any friends or relatives who are not used coming to Church).
The marriage will be recorded in the parish sacramental record, and you will receive a certificate of marriage, and the annotations on the new license.
sorry did not realize this was an old thread already answered, I am losing it, but then, you knew that.
congratulations anyhow, tell us how it went, with pix if possible.