>Question #1: Is the quality of the glass on the 18-55 about >the same as on the 55-200?
>Question #2: Do you agree that I am unlikely to get >professional-looking photos from my 18-55 and 55-200?
No! Even the kit lenses are optically excellent. While the Pro zooms and Primes are better the difference is smaller than most think.
>Question #3: If you were going to buy ONE prime AF-S Nikon >lens for general landscape use (and you already had a TC 1.4), >which would it be?
When I think of a landscape lens, I usually think wide angle which are not designed to be used with TC's including the TC-14E II. Without regard for budget, for an AF-S prime, it would be between the 24mm f/1.4G AF-S, 28mm f/1.8G AF-S, and 35mm f/1.4G AF-S. Good Luck and Enjoy your Nikons!