Drilling won't work! that little case is hardened so the bearings roll 
without indenting it. Get a washer the same size, ~<20 mm, and grind two 
flats on it to make an oval. This should now fit into the shell, just toggle 
it. You can pull out the shell by putting a long bolt and nut through the 
washer, and tip/toggle into the shell so it rests securely against the rim. 
Bang it out backwards using a Cresent wrench as a slide hammer, just don't 
hit yourself in the face as it comes free! Pack the new bearing well with 
grease before mating the transmission shaft.   tim s.