None of the Nikon digital cameras and few of the AF models will use your present lenses. You would also lose the benefit of mirror lockup for your 100-600 lens. Flash is also not real compatible.
So, I think your best bet would be to get a decent fixed mount digital to learn about the technology. Whatever you buy today will be way out of date a year from now. The technology is still in the rapid development phase and is changing weekly. Nikon, Olympus, Canon, Fuji, Sony all make great digital cameras.
When I bought my N80, I kept my FE-2 because it still works with all the AF lenses (but not vice versa) and it has lockup. Unless you want double inventory, you need to look at compatibility. Also, the digital sensors have surface charge and make great dust magnets. So it's not a good idea for most of us to change lenses as it lets dust into the body. It's a good argument for a fixed mount digital camera.
Just my 2 cents worth.
