I may have phrased my question incorrectly. I already knew you can use a separate Apple ID for iCloud and for iTunes/App Store. What I was asking is if I ALREADY am using my iTunes ID as my iCloud ID, when I click "Delete Account" on the iPhone if it really does COMPLETELY delete the account. I have about 200 gigs of videos bought on my iTunes account and I was concerned that deleting the iCloud account on my phone would likewise completely delete that Apple ID completely and I would completely lose access to all these purchases. Because all I wanted to do was disassociate it from the device, not actually DELETE the account, you know?
Well, I crossed my fingers and prayed last night and tried anyway, and phew, I can confirm that it did NOT delete that Apple ID. It still exists and all my purchases are okay. This was what I was worried about. Sorry for phrasing my question poorly.