I hope all is well, It comes down to planning, as so many things do. Take a look at this blog post to address your first question, as it walks you through the step by step to perform the upgrade, along with setting up and using the CodeIT Repos, which will get you around some of the issues associated with install/upgrades and ensure that you have the latest updates.
For Question #2, take a look here, as this is the CentOS MAN file for ACls, and has links to all of the sub items that you will want to examine. There are two types of ACLs you will have to figure out and use:
- access ACLs - the access control list for a specific file or directory
- default ACLs - can only be associated with a directory; if a file within the directory does not have an access ACL, it uses the rules of the default ACL for the directory.
Good Luck ... Let me know if you need anything else.