If you're doing night photos, get a remote. They're dirt cheap and work awesome with "bulb".
I also have an sb600 flash and it works great (sometimes a little too great...but I'm still learning how to use it best). Especially for TTL based fill-flash. I can have all the lights turned off in my room, stand 2 feet in front of the camera and still get decent exposure of both me and the background. You'll also need either this flash or the sb800 if you want to get into Nikon's CLS. These aren't so cheap.
Remember to multiply your focal length by 1.5 to get the equivalent focal length (a 50mm prime works like a 75mm prime). Other than that, any older AF lenses you have should work fine (even 30yr old manual lens work, though you won't be able to meter through the lens).
Its a whole other world. If you've been shooting film for a long time there are going to be parts that you absolutely hate, but the opposite is true too (you'll end up loving other things like instant review and only paying for developing on images you truly want). Keep an open mind and remember that even though it looks like camera, it doesn't always act like one (a handheld scanner is one analogy I've heard).
