Agitator repair parts

The top part of the agitator is not woking properly - so I am going to order the agitator repair kit for my washer. How do I know which one to order since it comes in 3 different sizes? Once I have taken it apart should I replace the thrust washer between the upper and lower parts of the agitator? Is it necessary to replace the agitator clip, washer and spanner nut in the lower part of the agitator? The lower part of the agitator seems to be working fine.

Thanks for your help!

I cannot get your model number to come up, but if you call in the order to APP they will get you the right part. Have your correct model number and serial number.

You probably only need to replace the agitator dogs themselves, which are common to all models. That other stuff should be ok.