cd player swap

I have a bone stock 07 silverado with a plain radio. Would a cd player/mp3 from another 07 hook up and fit into my truck?

yes, but it will have to be setup with a tech 2 at the dealer, the radio will be in anti theft lock, and the bcm won't recognize it until it is programmed for it. If you want another radio, the easiest alternative is probably just to go aftermarket.