With flash prices where they are right now I'd recommend getting a 128MB card. As far as the Kodak lenses go, I can't say. I haven't tried any of them. I'd definitely recommend getting a second battery and the quick charger.
The best shots you will be able to get of aircraft with this camera will be when you are close. I haven't had much luck getting good enough photos for airliners.net unless I'm really close to the plane (gate shots).
Until I can afford a digital SLR, I still prefer my 35mm. Don't get my wrong, the DC4800 is a great camera but it just doesn't meet my needs for aviation photography (which is not what I purchased the camera for anyways).