Not sure about aligning to a poly normal... Do you really need it to be so precise that you can't just eyeball it? --I suppose it will depend on what you're doing.
You can create a new perspective camera and make it ortho, though, that's fine (each camera shape has an ortho/persp attribute you can toggle). In order to make sure the rotations line up just right, you might want to do this...
Create the plane flat on one axis. Now align your new camera so that it's looking right down that axis. Now make it ortho. Group the camera and the plane together, move the group rotate pivot to the center of the plane, and voila. You've now got an ortho camera permanently affixed to your plane. Move the group around until your plane is where you want it to be, switch your view to the grouped camera, and you've got an ortho view in exactly the right place!
There are probably easier ways; this is just what springs to mind.
Good luck.
-Steve