Couple links here, Bob, that worked for me.
Can be a bit fiddly, but you've likely already got the skills with your career experience. Some 22ga wire soldering required and do be careful removing the solid rivets holding the sensor to its base plate. Same care required when refitting the new sensor. Tight working area doesn't begin to describe the work space.

Several shims, washers and fiber spacers inside the can. They will often stick together during disassembly, then separate when you toss the
"single washer" onto the bench.
Jeez, wonder what order they were in?I've rebuilt four bean cans, mine plus the three I've bought around the www. One was truly butchered by the PO so took mucho love to rebuild. A spare is handy to have on longer rides. Naturally, after fixing my own can, I've never had another problem. Go finger... uh, figure.
Monte
http://robfrankham.co.uk/bike/replacing_the_hall_effect_sensor.htmhttp://maniac.deathstar.org/%7Eflash/ig_trig.html