Sounds good. You probably have a bit of time to work on it with your long winters.
I doubt you will have to rewire with only this unit being added. The larger the screen the more it draws. If you should experience extra draw you can reduce the screen brightness.
I know some guys who run as many as 5 large screen units. There is a big juice draw with all of them on at the same time.
I will buy size 10 wire and make 1 solid run from the battery to the bow, with an inline fuse. I will check to see what amperage the fuse should be.