Classic/Antique Car Repair: mg td oil leak, engine oil leak, cam shaft

Question
Hello, My wifes 1952 MG TD is in great shape other than a major engine oil leak.  Great oil pressure and smooth running engine.  Clean oil drips mainly from where the starter motor shaft passes through the housing of the ring gear.  It is not dripping at the cotter key hole at the bottom but that could be plugged with dust and oil inside.  Are there options for oil leaking other than the rear main bearing seal?  Can I remove the gearbox and flywheel without pulling the engine on this model?  
  Hoping for an answer that doesn't involve the word "crankshaft",  Mark

Answer
How about the word camshaft, or rocker box cover. The plug at the end of the cam shaft could be leaking and the oil could be coming down the back of the engine from the valve cover or as the English call it the rocker box cover. The engine and transmission need to come out as a unit.
Brad