Enjoying the game so far, I'm about eight hours in and still running around the first area. I've got two trophies and I'm just wondering, after talking to the people for whom those trophies are relevant, should they disappear from my inventory? If I hover over them the tooltip says 'trophies can be turned in for a reward'. Should I hang on to them after turning in the quest, or just sell them? If so, who should I sell them to?

Also, regarding Geralt's witcher swords, I've been hanging on to them because I read you can upgrade them over the course of the game (but I've been replacing them with better swords as I find them). Is this true, and how do you upgrade them?