I recently pulled the headlight off of my 2008 Fatboy to replace it with the freight train nacelle. The only way that headlight comes off completely so you can pull off the tins behind it is to cut the headlight wires.
Not sure if it's any different on a 2010 Lo, but you may want to go on the HD site, look up the freight train nacelle for your bike and look at the installation PDF. It will tell you exactly what you need to do to remove the headlight and tins.
2008 FLSTF - Traded 9/2015