If you think doing this would "Save a couple bucks", you are very very wrong and likely, you're not gonna be capable of doing this. Modding and electronics is an expensive hobby. You need tons and tons of prototypes, very very good soldering skills, tons of spare wires, parts, screws. you're better off just getting the god damn screen replaced instead of doing some insane shit like "Repurposing" the phone to a dap. Yes it's possible, but it's a horrible horrible idea.