You'll definitely get faster autofocus from the AF-S lenses, but where they really excel is when you're tracking a moving object: something I suspect would be of real value to you when photograping motor sports.
Just to add to your dilemma, }> have you considered the AF-S 300mm f/4? It can be used with the TC14E to take it out to 420mm. B&H sell it for about $1200, so it's somewhat less expensive than the AF-S zooms.
It looks like the chief advantages you'd gain from the D1 would be the instant results and the ability to take large numbers of shots at virtually no cost. What you'd lose would be the very high performance autofocus (which would undoubtedly be of use to you), the higher optical quality and the ability to use 3D matrix metering.
At the present time it looks like the lenses may be your best bet. The price of digital SLR's will fall far more and far faster than the price of such quality lenses - and you're far less likely to want or need to upgrade them in the future.