RE: shooting a left handed gun right handed
There is always the chance that cap fragments can fly off. I'd hate to count how many times I've been cap sprayed. The one thing you will have to contend with is of course the crossing over to cock the rifle. I have a friend who for years shot right hand rifles left handed. Finally he bought a left handed rifle. I asked him if it was better and all he said was it felt more comfortable.
Flintlocks are a whole different story because you have the pan flash coming right infront of your eye.
Wear shooting glasses and you should be all right. Still, there are a few left handed rifles out there from some makers,and some in the auction sites which might be a better way for you to go.