broke off crankshaft positioning sensor how do i get it out to replace

This is a common problem with GM's Try chopping , drilling and picking away at the sensor ( it is only plastic with wire and a magnet ) Once you get out all the pieces , it is a good idea to clean the hole with some fine sandpaper. put a light film of silicone grease onto the new sensor , when installing it and lube the bolt hole too ( for sensor bolt) this will ease removal of it , in case it ever gives you further problems