Breaking on the way in is OK - they usually back out pretty easy. Learned a cool trick from a mechanic that broke a head bolt going in and didn't want to pull the head. You need a stick welder. Remove the flux from the tip of the rod, position it in the hole on the broken stub, then flip on the power momentarily. The stick welds to the stub and you can just spin it out.
If you do decide to drill, pack the hole with thick grease and put a ring magnet (there's got to be one on the fridge) around the bolt hole. Tape/mask the exposed crank just in case. Drill slowly. You might not have to take it apart to clean up all the filings.
