I've done a few weddings, always for friends or friends of friends. So here's my advice: Shoot the F6, put it in program mode and use the flash. You want as few mistakes possible and you won't have as much time as you think to change lenses or make adjustments. I would use a 50mm AFD or a Tamron 28-75 2.8. The F6 is a fantastic camera and you can just let it do it's thing and you do yours. It's autoload so you won't have to fumble about with the next roll. Have the Leica in your bag as a back-up just in case.