IMO, you'd start with the basics in level one. The level three stuff supposedly won't even work until the basics are implemented, so it seems like you'd want to start at the beginning.
And I can attest to the 'doing everything at once'. In an excited flurry I made a bunch of changes ASAP after I got my course. Did something every day, and was feeling the effects of the stirred-up chi for a good two weeks, on top of some other stress I was going through. Not fun! (Though after finding out the stuff I was feeling
was chi, I was
so relieved...) So, yes, pacing yourself is a good idea, too. ^_^
Best of luck!
