exchange mother board on a live unit ?

i plan to buy a galaxy note 3 live unit.
If i change the mother board will it work as a real working galaxy note 3?
or do i need something more ?
can i just buy any galaxy note 3 mother board or do i need to think of something ?

Is screen bleed common? Should I exchange for another?

My MXP has yellow screen bleed in the lower right corner. I can't see it on moto display notifications but if I'm in a darker room with the screen brightness at 50% or above, I can see it on a dark background like the app drawer. I suppose it isn't a big deal and I don't even notice it in most conditions but I was wondering if the majority of us have the same issue. If it's not common, I'm within my window to exchange at Amazon. Thanks for any replies.