Well, one interesting approach might be to make it so that this long paper you are writing is about the old paper. Let the old paper be one of the subjects of this long paper. You can write about a time when you wrote this paper, and then you can quote pieces of it.
You can use italics to show the old essay. You can make this whole new paper all about how the current you is reflecting on the old view. It can be great. It will be like a close reading of your own work.
However, if it gets complicated, another approach you can take is simpler: Read through the old paper, making improvements everywhere you can, and when you get to the end, keep writing. If you ordinarily use caffeine, this is where to do it. It is better not to use caffeine, though... At the end, go back and add a new intro. A nice intro that introduces the whole thing, whatever it has become.
Kevin, EssayForum.com