There are many local salvage yards where you can possibly get a used transmission and transfer case. Of course, you can also check with your local Chevy dealer as well.
Here is a good website that has connection to various recycled/used parts:
The prices will vary depending on the condition.
Also, if you have it installed in a shop the cost will depend on their shop rate. On these trucks the typical labor time is 9 hours.
I have attached the transmission replacement procedure below for your reference.
Please let me know if you have any questions.
Images (Click to enlarge)
Tuesday, March 8th, 2022 AT 2:24 PM