If, as you say, the problem is no display AND no audio, it sounds like your Sansa took quite a beating.
I have no idea how much people would charge to diagnose and fix a problem like that, and to be honest it sounds more bad than good, but maybe you could:
a) see if you can get your music off the player when hooked to your PC
b) assuming 'a)' is successful, look online or locally for someone who will attempt to diagnose/fix the problem. Ideally you want a 'fix it or no charge' deal. I wouldn't recommend just buying a new screen, as it seems your problem is more severe than simply that. The lack of audio might be a simple problem, but the way you describe the screen as utterly shattered makes me think that you may have to say goodbye to your Sansa.