Hello, I am new to this site and need help

I am getting ready to paint the ceiling in my family room and have not a clue what type of roller to use or type of paint. It is a vault ceiling. Also, a couple of years back, we had a very bad storm that loosen some shingles on the roof (which I had fixed) however, a small leak occurred due to this. I painted over the leak and did not know that I should not have put so much pressue when painting it, NOW it is like a small smooth section. I was told I could spray some popcorn stuff on that small area and it would be fine. Do I do this before I paint the ceiling or after? I really need to know how to paint this ceiling before I paint the rest of the room. Thanks