Why is the Trinity so important? Is it okay when a priests changes some of the words at Mass? Should we tell our kids about our pre-marital sins?

• Marilyn 9-years-old - Why is the trinity so important? Why don’t some people believe in God?
• Barbara – My priest changed some words during Mass. Does that invalidate the Mass?
• Tim - I haven't been to confession in 20 years. I would like to go, but when I go, how specific do I need to be with my sins?
• Gabriel - How can I explain my relationship with my wife before we got married to my kids? How can someone maintain boundaries in a long distance relationship when they are visiting each other?