Watch how tiny problems we ignore today always blow up into massive headaches later. That filter cover is just the latest lesson in a long line of them.
Yeah, the "rust glued it tight" part is a real pain. I read a trick once about using a thin lubricant like WD-40 around the seam and letting it soak for a good half hour before you try to pry it. The key is getting that stuff to creep into the rust, not just spraying and forcing it. Sometimes you gotta tap the edges with a rubber mallet too to break the seal loose.