Trek has changed their FX/7000-series designations a couple times;I think that's an '04. Trek's archive doesn't show disc models for that year,but I know for a fact they exist because my friend has one. And I'm positive those are 700c wheels.

As to it being worth $200 more,yeah. The brakes and shifting are def going to be better than the older bike's,and it prolly has a wider gear range as well. The Trek's rear is going to be a freehub,which means changing your gearing(cassette) is going to be much easier due to parts availability,not to mention it can be changed from 8 to 9 to 10spd without rebuilding/replacing the wheel. Basically,the Trek is a modern bike with modern parts,plus it should have significantly less mileage. If it fits you,I'd go for that.