Should my thesis be changed? Asperger's syndrome is a milder version of form of Autistic disorder. The difference is that these...

If your thesis statement is the last sentence of your introduction, it is probably fine.  I'm not sure why you didn't capitalize and italicize the book title, however.  Your thesis will work well as long as you rember that you are creating a two-part argument.  You have to address the hurtful aspects of Asperger's, and then you have to address the helpful aspects of Asperger's.  You need to be sure to use specific examples and evidence from the text to support both arguments, and you need to be sure to write the entire paper in present tense.  Good luck!