Ray - my entry went into the mail this evening.
Scrad, don't worry about the positon of the balls and dirt. It will be fine. You can use the white covers if you want, but they are not necessary. The most important thing to do is sand both sides of the diff ring flat on a smooth, flat surface with 600 paper. That will equalize the force on each ball and give the balls a very good surface to ride on. You will be surprised how smooth it is when done correctly and the times you can run it without rebuilding. Oh, the next most important thing is to use a new outside bearing when you start. It will last a long time, too.