Lessons are a good idea. They are vital for beginnners, and can be useful at any stage of skiing or boarding. World Cup racers have coaches, so they think they still have stuff to learn.
Lessons when you start will get you into good habits. A lot of instructor time with intermediates is spent getting people out of bad habits. It is best not to get into them in the first place.
Most resorts offer a variety of lessons. The two main divisions are class and private lessons.
Class lessons can have up to 12 people in them. The attention of the instructor is divided among all the class members. Class lessons are a way of meeting people. Watching other people ride and hearing what the instructor says can help you understand what the instructor is talking about when she or he critiques you.
Private lessons are more expensive, but they mean the instructor is devoting all of his or her attention to one, or a small number of people. Private lessons are good if you have a single intractable problem. In a class an instructor may not have enough time to devote to fixing that problem. You can also reduce the cost by taking an "off peak" lesson, these are usually early or late in the day. Most places it is 9am or 3pm for cheaper rates. 9am is usually the better option as you aren't tired and the snow is usually in good condition and you have the rest of the day left to practice what you learn with the instructor.
Many resorts offer clinics in particular areas of sliding. They have women only programmes, and a whole lot of other stuff. Each has its place.