I can't see how installing a scenery would have any effect on your instruments. The gauges resolution is tied to the global maximum textures size setting, but the installer surely won't touch it.
You can set it to 2048 or 4096 textures size in the Addon Manager, but this won't increase the instrument panels, since the vast majority of them is made at 1024 size anyway so, unless you put the texture resolution slider to be LESS than 1024, there's no way the O'Hare installation could have anything to do with this, since the minimum size the Addon Manager would ever set it, is 1024, and that's already the maximum resolution for the vast majority of panels out there.