Ok, don't worry about the ribs - that's the least of your problems.

As far as the servo tray goes, just leave everything the way it is.

But as for that spar, you will need to glue a piece of the same size into the gap, and then add a second piece that is AT LEAST twice the length to the top side of it (The side away from the covering) You'll need to remove some of the center sheeting so you can clamp it to the spar, and you'll need to cut out a slot in the two ribs for it.