Both guys are "right". Some bearings are vacuum-packed in a "clean" environement, and need no "prep". Others are packaged in an oil-skin type paper, and do require washing before use.
ALWAYS inspect them for flaws or damage. Slight "nicks" can be rubbed out with scotchbrite or REAL FINE steel wool, and washed afterward.
Agreed, King makes a good product. We tend to allow a little more clearance in a rebuild than "factory specs". Shouldn't present a problem at .003".