There are charts out there that spell out the functionality of the different bodies with the older lenses. Look on Nikonians or
Thom Hogan's Nikon Field Guide and Nikon Flash Guide for them. Thom's site is also good for Nikon reviews, as he is an actual bonafide Nikon guru.
IMO, skip the D700 for now. Lots of hype for "full frame" camera bodies, but it's a mixed bag. Having the 1.5 crop factor of a D300, for example, can be a huge advantage. An 18-200 will function as an 18-200 on a D700, but on a D300 you essentially get more "reach," as it functions as a 27-300. The 1.5 crop factor body is a MUCH cheaper way to get more reach than longer focal length lenses.
My gut tells me the best body for you to get is a D300. It's a big improvement over the D200 and is of the more robust metal-framed family with weather-sealing, amongst other advantages. I wouldn't exchange mine for a D700, I'd only get the D700 in addition to it for the reasons above. The 1.5 crop factor bodies are called "DX" vs "FX" for the "full-frame" bodies. DX lenses are cheaper and full-frame lenses are less critical on a DX body because only the heart of the image is catching the sensor.
I'd say go to eBay as a last resort, unless you buying from someone reputable like Cameta Camera. Some of the reburbished bodies can be killer deals. First choice for used would be
Buy & Sell - FM Forums IMO, as you're dealing with a camera buff and buyers and sellers there have often acquired reliable feedback ratings. The
Nikon-mount SLRs - FM Forums forum is also an excellent resource.
Lens-wise on a DX, I'd say hands-down the basic lens if you want top quality is the 17-55 f/2.8, but it's no bargain. The Tamron 17-50 f/2.8 is 90% the lens for 35% the price. Add to that the excellent quality, bargain Nikon 70-300. Good wider stuff is out there, but it's not critical to have it unless you have a specific need. Nikon's entry-level zooms are all very good, and some are better yet. You'll generally lose image quality for the larger range you take.