Here is a wonderful article that will help you harvest your new crop.
Welcome to gardening!
yes it will, at times all I do is grab the whole plant and cut off the lettuce that I want, if you keep it watered it will continue to grow, also if you let a few go to seed, they will sprout up next year.
I have done that and I haven't planted anymore seeds as there growing all over ,and I just harvest what I want.
Hope that answers your question