Sounds like a bum deal. The Mercedes service literature describes the hollow camshafts as "very breakable", and require special care taken during installation. The 104 is an interference engine but if the camshaft broke during install, the valves could still be ok depending a lot on where it actually broke. If the broken piece isn't holding any valves open very far there may be no damage. I'd source a camshaft, install it, and do a compression test to see if any valves bent. If the head has to come off I think most shops bill 12 hrs. If it were on the other side of the Rockies you could bring it to "my" shop. The boss doesn't call me "104" for nuthin'