I need to remove and repair speedo head on a 1984 380SL. I gave it to a shop as I had not the time or experience. Shop is telling me that they cannot loosen 10MM steering wheel bolt to remove steering wheel to proceed with repair. They, of course, tried long breaker bar for leverage. Mechanic is concerned because allen head bolt is not that deep and is afraid it will soon strip. Any ideas short of drilling it out. Thanks