What is the difference in parts AP2142342 and AP2153302 or do I need both?
Answer Hello Ronbach,
You will only need to order 5308950197. This kit contains 5303279394 so it will not be needed.
Does Part number 26 on the Transmission contain the items of #17, #18 #19 & #20?
Answer LuAnn, the retaining ring  (item 17), the washer 5308002475 (item 18), the thrust washer 5303161226 (item 19), and the lower lip seal 5303161173 (item 20) are not inlcuded in the tub seal kit 5308950197. They are only available separate. Thanks!