^^^What He Said^^^ on both points. You need to replace the failed "Lid" and use the upgraded polycarbonate ones as linked there in Amazon. Just please be sure to click on the "CAMCO Match Your Hinge" image on the Amazon page and order the correct one. You probably don't know the Brand of your Vent Assembly, but the correct Lid can be ID'd by the detail images of the Hinge Area.
I believe MaxxAir is the best of the Covers. These keep rain out so you can open the Lids in the rain, store the coach with ventilation, etc. There are other decent brands too, and CAMCO is one. For that, I suggest you choose Covers with some form of Easy Access feature. Last time I shopped, that was standard on some MaxxAir Covers but not on the basic ones. By Easy Access I mean you can swing the Cover clear of the Vent to clean, repair, etc. No big deal, but worth doing.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB