can anyone other than the Mercedes dealership fix the ignition switch in the c300?

Why would you take it somewhere else when it's likely a warranty failure? I would assume you're still underneath the factory warranty period? It's such a new vehicle comparatively; so why a non-dealership repair shop? Not knowing what specifically. needs to be done, it's impossible to know if programming is needed. Once the vehicle is assessed then you can get an answer -- so, you can see another shop if need be: Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops