It is not as difficult as it looks... Depending on how your router is set up; like, is your spindle turned on by the controller or manually... if you turn it on by hand then you don't need the M codes to turn it on and off. Some controllers won't do circles, they need to be generated in two half circles... Try a simple generated code with just a couple of lines and curves to see what is does.
You can also edit the Post-processor by hand; go to C:/CopperCam/ISO.ppf and open it up with a text editor. This is the ISO default Post-processor. You don't need to create/edit the Post-processor within the dialog box, you can just do it by hand in a text editor and save it under a new name. That is the way I always had to do it. You can open up anyone of the .ppf files and look at the difference between them, or edit and save under a different name. The Post-processor format in for all machines, you just need what works on your router...