Thank you. This got me closer, but I'm still not quite to my requirement yet. I now am able to populate data into the form automatically, but there's two problems, with screenshots below.

1) The user info being populated is the logged in user. The template I worked from was built to accomplish this, so I'm not shocked there, but I can't find a solution to instead have the reference be from my Reference Field, "employee_to_be_terminated"

2) I am getting data onLoad, but it should only be onChange

Script Include:

Catalog Client Script