Purging? That's a new one on me. Anyways, yes, the line at the fuel filter will automatically start draining the thank. After a few seconds of that, you might be best to drain the entire fuel tank (there is a handy drain plug on 1200 tanks) and put clean gasoline back in. If you drain into a clean bucket, any dirt or water will settle to the bottom of the bucket (very visible). Then just pour the top part back into the tank.

Yes, you'll just need to crank the engine a bit before it will fill the carb bowl and fire. You might consider disconnecting the coil and cranking until you see some fuel in the carb sight-glass.