From a senior reader…
My fiancee (age82) and I (age 76) are both widowed and lifelong Catholics. We know what documents we need, but what other church requirements must we go through before marriage.
You should have your baptism certificates, which will indicate other sacraments you received, including your marriages. You will also need death certificates for your late spouses.
However, the first step you need to take is to go to your parish priest. He can get everything going for you. He will guide you through the steps.
My grandmother married again in her late 70’s. She too snagged a younger man. I think he was 75.