Transmission replacement instructions please?

It sounds like there is a leak in a seal or valve body. Unfortunately they are most likely correct that a unit will be easier and almost the same price.

Here is a guide that will help with this:

https://www.youtube.com/watch?v=3vJAojsrfuU

Below is the process from the manual that will help with this. Thanks

Hello, I'm Danny.

Here is the information you requested. Usually what we ask you to do is provide us with the stored transmission codes to help properly diagnose any transmission issues. If you perform a CAN scan on your truck it checks all vehicle systems to read any stored codes in the computer like transmission codes you mentioned. Here is a tutorial showing how to perform a CAN scan on your truck:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

If you choose to replace the transmission here is a tutorial for you to view showing how to remove and replace a manual transmission which is similar to an automatic transmission:

https://www.2carpros.com/articles/transmission-replacement-removal-manual

I've attached picture steps below on how to remove and replace the automatic transmission on your truck. Hope this helps and thanks for using 2CarPros.