i don't know of any tool used to create screens, helps a lot if you write your own extension of the mainscreen class and use it as a basis though.
as far as eclipse and the JDE merge i have no problems as long as i work my files in a single project. pretty sure you can go further but i am a bit lost with the ant-files.
just make a search for eclipse in the forums and you'll digg out the step-for-step guide which is quite easy to follow even without knowing what you are doing