fuel leak

Had a not so pleasant surprise today while cutting the belly board opening in my Q2. As soon as I pealed the skin away I smelled fuel. Thier has not been any fuel in this aircraft in over 15 years yet, the foam was wet. I believe it came from the fuel tank drain area, don't know this for a fact. Now I need some expert advice on the repair. I am posting a couple of pictures of the area. I marked the forward edge of the wet area I don't now how far aft it goes. If you have an idea about this please let me know