My oil level sensor leaked on my 560SL. It took two attempts by my mechanic, but he successfully sealed it from the outside. I know that he either loosened it or removed it from the outside and thoroughly cleaned it before applying sealant. It has been several months now and the leak hasn't reappeared. The information Chuck provided is the proper way of actually replacing the factory seal. I was quoted $1600 for this method. My mechanic performed the method described above for free.....guess how hard this was to decide!
