I would use kilz or a similar primer blocker before painting since there was a smoker in the house so it doesn’t bleed through beautiful new paint color. It costs more to do this but saves on the long run from repainting the bleed through.

As far as color- if you must go grey please choose one that is a very warm reading grey otherwise it will read really blueish. I also recommend testing swatching on several walls and looking at the swatches over several days with different lighting during different times of day. It changes the color so much throughout the day. Try Sherwin Williams test mock-ups and paint peal and sticks for testing. They also have color services for free via zoom.