The best way to check the old bearings is to clean them up, blow them out and look at them. Place them in the races and check for any side to side movement as a whole. Any clicking or movement is not good. If you see any nicks, scratches, rough spots, etc., they will not last long.
Pack them by hand. Take a huge handful of grease and force it into the cavities, again and again until they are full of grease. I suggest latex gloves
Jeff
