I would say that it depends entirely on your skill level and what you are trying to do.
To begin with I haven't taken their class on SEO but I have taken other classes from ED2go and they were very well done.
There is a tremendous amount that can be gleaned from the net for free. To some degree just searching it out will give you some idea of how SEO works.
Go to any website that ranks high and look at the source code (in the menu bar View / source).
You can see just what is there and how it is written.
I think you need to have at least some knowledge of how HTML and the related codes work in order to understand SEO, but that is just my opinion.
I would say that ED2go is probably going to offer a good class and it should say in the synopsis what skill level is appropriate.