Nearly killed myself in the Dart today! :(

I would get a new seal first, then pull the tank out. Unhook the battey, disconnect the sending wires, Remove the screws in the filler tube, also unscrew the rubber seal where it meets the floor. Probably want to drain the tank, probably siphon it out. Then, unhook the rubber fuel line, then loosen the 2 fuel strap bolts and drop it out. Pretty simple, wouldn't hurt to spray some wd40 on those strap bolts. Then, with the tank out you can repaint it, first see if there is any crud inside, (or parts of the old gasket) could get it cooked out and the old paint would come off too and make for a easy repaint. Also check to see if your fuel line/hose at the tank is good on the car.

You could probably replace the seal with the tank in the car but this is what I would do, you have a nice car and it should be done right. Glad you and your car are safe!!!