Hey SC_CKD, welcome to KF. I'm pretty sure that there are a couple CKD people on here, but I personally have no experience with it. It's Chuck Norris's art, right?
I've read Boxer's Start Up, it's a nice read.Another good boxing book is Box Like the Pros By Smokin Joe Frazier. It's very similar in content to Boxer's Start Up.
I think that having doubts are normal and should be considered to some extent. Obviously you shouldn't spend most of your time worrying, but I think that if you're having doubts, you need to decide if they're valid or not.