Replacing evaporator core?

The dash has to dome out, then you pull the HVAC housing. From there you split the housing and remove the lower shell and then you can get to the cores. No way to do it with the housing in the car. Wish there were but there isn't because of the way it's designed.

Ok, thank you Steve. Do you happen to know anywhere I could look at a step by step for the entire process?

The easiest way is to get a limited DIY subscription from Alldata or Mitchell. You then have access to the same info as a shop for the time you selected. BUT it's also not hard to start at the top and print the data to .pdf files for use later
https://www.alldata.com/diy-us/en or https://eautorepair.net/
Look over their examples and then start printing the info out. The advantage of that is that I'm used to doing the job and might miss a step that is in the book.