Do a Google search and you will find a number of YouTube videos and articles on other sites about dismantling Nikon lenses. While you probably will not find one specifically about the 18-200, my guess is that there are common assembly techniques and you might get some guidance.
Good luck — I think you will need it!
Jon Kandel A New York City Nikonian and Team Member Please visit my website and critique the images!
Anyway, I started to tear down further, leaving the internal lens assembly where it is. I could remove the outer shell. Then I found the location of the loose screw. And I could also repair the copper bolt.
But next to the loose screw, one sliding path is broaken. I have put a picture in my gallery. It is in aluminium, so glue isn't possible. With dental aid I was able to fix it.
I was able to reassemble the lens and everything works, only autofocus is stiff. I assume that fixing the broken part has created more friction. It is also impossible to manualy focus. The ring slips like it does when you reatch the end of the focus.
So I need to know if the sliding path is always broaken? If not, I need to smoothen the repair of the broaken part.
About 55 years ago I took a Pentax manual focus lens apart. As I remember, I didn't have a good reason -- I just wanted to. I had to package it carefully and take it to a camera repairman, who reassembled it and charged me what was then an exhorbitant price. I still count it as tuition in the school of hard knocks and have never taken another lens apart again. I wish you better success than I experienced!