You can look at this scenario to see how to remove the control panel. The code that removes the controls is in the started() method in Screen (also calls the trim(... method).

I don't really know about making a Greenfoot scenario full screen. I know how to get the dimensions of the screen, but I don't think it will be the way you want it to by just setting the World dimensions as that. I was planning on reading Lesson: Full-Screen Exclusive Mode API sometime in the future, but I have no idea if it will be any help for what you want.