Personally, if it were me, I would not drive it. On camshafts, the surface is hardened. Once you get past that you are into "soft" metal that will wear much faster.

Even if nothing catastrophic happens, you will be dumping metal shavings into your oil with every revolution of the camshaft. Your filter will probably catch most of them, but they the engine will wear at an accelerated rate. Flushing is a good idea, but you will need to do it frequently IMO.

Have you checked with Phil or your local MB Parts Department? I would think that you would have better luck finding a used engine than just a used camshaft.