AspectJ and its Use

Hi,
I recently started using AspectJ and need some advice regarding the following

1) Are aspects really non-intrusive? I wrote a small class (Test.java" and an Aspect that works fine but when i reversed Test.class i found some aspect code injected in it.

2) I want to use Aspect to work on my existing application (without recompiling my existing source), would Aspect still work for me?

I am not too sure if this is the right forum to ask !!

thanks in advance
-Hari