How to free up fresh air vent door?

Thanks for the replies everyone. I was able to get the latch freed up by tapping on the handle with a hammer and working WD-40 into it. I ended up grinding of the hinge-to-box rivets with a dremel and once I had it off the box I was able to get the hinge freed up as well. I think I’ll still buy me some evaporust and soak the door and hinge assembly before I rivet it back on the box.
I just this weekend took apart the door hinge and latch assembly sand blasted and then hammer and dolly every thing straight and ready for paint, I an currently sourcing rivets to put everything back together but the kicker is the tool used to chinch the rivets tight, the rivets can be purchased from eBay the same type they use to restore old Tonka trucks, I will post pics on progress