It can be painted, follow paint manufacturers directions for repairing the metal surface and painting.
I cut mine to 10.5" diameter in both the exterior and interior walls.
Hello PiedPiper! Thank you for your recent inquiry with The Home Depot. We have this damper available in 12 in. Please click the link below to view the 12 in. Round Galvanized Wall Vent with Spring Return Damper. http://www.homedepot.com/p/Speedi-Products-12-in-Round-Galvanized-Wall-Vent-with-Spring-Return-Damper-SM-RWVD-12/202907289 We appreciate your business and look forward to serving you in the future. Thank you for shopping Home Depot.
It does not include a screen, but a spring loaded flap instead. I was thinking about using a wire mesh screen (used on windows to keep bugs out) but didn't do it. I'll see if bugs/critters enter past the flap in the spring/summer and will decide then.
There were no installation instructions when I received my order. It may be helpful to look on the internet for videos of how others installed an exterior vent.
The spring loaded damper is removable.