Removing beading

Find one that will give pretty easily, and work your way around. I'd try to start with an outside corner, if there is one in the room, try to get something thin behind it such as a paint scraper or similar, and gently use the beading as its own lever. As you work your way around, you can use something heftier such as a small nail bar. For the more stubborn nails, you might find that they pull through the beading - pull the nails left behind afterwards and fill the holes in the beading with filler when you're reinstalling them.