Best Practices to create/image Prod to Test/Dev on identical VPS and sync using different DNS/IP

This is high priority as we want to go live on e-commerce site 6-18 and need this to make a large number of changes and don't want to "test" on our production server. I currently have two identical hosted VPS instances and would like to know the steps and/or best practices to create an "apples to apples" image for the purpose of installing patches, upgrades and configuration changes on the test/dev box prior to implementing them on the production server. I am running Prestashop and know how to make the application, php and mysql changes however I am new to cPanel. I need a definitive guide to re-image development from production as needed using one of my many domain names. I bought an SSL certificate for the dev box so I could have as close to an identical configuration on test as I am running on production. I need an identical VPS setup (IP, SSL and Hostname exempt) so I can have a baseline machine to see how any changes will affect the Production VPS environment. I know I can't be the only person to request this and sorry for any repetition however I can't find any good posts on this subject other than we're working on it. There has to be an example of how someone is currently accomplishing this. I can find the raw files that I would normally change but I know that if I don't use the WHM tools then the changes will (probably) be stepped on and changed the next time I use easyapache or other cPanel/WHM tools. I have some other admins on this box that required cPanel/WHM. I appreciate the high level guild to accomplish this task as I don't need screenshots or step-by-step detailed instructions in order to make the requested changes. Thanks in advance! James Stepp