[Q] how to remove CARBON ROM completely and replace with NEW ROM

Hey everyone,
I'm creating this thread today to try and find some much needed help regarding my rooted HTC One m7 that currently has the custom ROM CARBON installed. I have a couple ways I know how to replace it with a new custom ROM it's just that I do not want to reap the repercussions that might come with doing them the way I know how. I'm not very familiar on how to backup your personal data and apps without knowing forsure that I didn't include some bits and pieces of my current ROM inside of the backup somewhere. As i would assume if that were to happen, it would most defiantly mess everything up when restoring it back onto the new custom ROM. If someone could shed some light for me on how to completely unistall my CARBON ROM while being able to save all personal data as well. Along with instructions on how to go about downloading and correctly installing a new ROM onto my m7 and restoring my personal data back onto the phone. I would greatly appreciate any help that can be provided. I will list my m7's information below. Thank you.
Current Versions:
-Android Version: 4.3
-Carbon Version: CARBON-JB-NIGHTLY-20130916-0659
-BUILD NUMBER: carbon_m7att-userdebug 4.3 JSS15Q eng.arrrghhh.20130916.065902 test-keys
-Kernel Version: 3.4. 10-cRtS-g32d1279
arrrghhh@nas #1
BASEBAND VERSION: 4T.20.3218.13_10.12.1718.01L