It's too bad because the Elbow Plane is a very difficult swing to master and takes an enormous amount of time and effort to become truly proficient. The Standard Patterns in the Yellow book are easier to master and will give almost any golfer a lifetime of pleasure on the golf course.
totally depends on the player and their ability. I know someone who made the change in a couple weeks of hard practice. If you take a 20 cap then you are probably right. I know I can do it and I am pretty much a hack.