Good question.
It depends on your purpose. If you are truly interested in mastering PhotoReading, if you want to take your skills to a higher level of performance, then absolutely take the seminar. What you take from the seminar, in part, depends on what you put into it.
There is no answer for how many times people go through the self-study. That depends on so many factors. No matter how many times you go through it initially, plan on revisiting the entire course or parts of it in six months to a year. You might be surprised at how far you've advanced.