National Marathon, DC

Ok, so I am getting addicted to exercise and the challenges of racing.  I have a list of goals for 2009.  One of them was to finish a 10 miler in 1:39 or better.  Now I am thinking about trying to do a winter 10 miler, and try to qualify for the National Marathon on March 21, 2009.  (This is 11 days after my 40th birthday).

As far as my current fitness level, I can easily run 3 miles in about 28 minutes.  I still have plenty in the tank at the end of a sprint tri, (I have done 3).  I feel like my endurance has always been better than my speed.  I have been doing the "tri-thing" for about 3 months.  I am training 4 days a week, and doing 1 or 2 mile runs on 2 of my "days off".  Before that, I was pretty sedentary.  I have gone from 11 minute miles at the end of my first sprint, to 9:39 pace in my last sprint.  I feel like I can maintain a 10 minute mile or better for a pretty long time.

1. Am I crazy? 

2. Does anyone have a suggestion of a qualifying race before the deadline for the National Marathon?  I am looking for a 10k or a 10 miler near DC.

Thanks in advance!