I trained control column right hand, throttle left. I was worried when I bought an aircraft and it was the opposite. I shouldn't have worried, it only took a couple of hours to get totally comfortable flying with the other hand. Now I can fly either way without really giving it any thought. I would suggest you take the time to get comfortable with both and that way you will not feel limited to which aircraft you can fly.
The left seat / right seat thing has been discussed here before and some said you can, some said you can't. I can tell you I was advised in writing by a previous Op's Manager that if the POH indicates PIC sits left, then you can only sit right seat if an instructor. Let the argument begin................