that is really weird, does that mean you won't get the rebate until month 10? lol
swapping drives on ps4 is pretty easy, but you will have to reinstall all your games. you should also backup all your saves to a thumb drive (or portable USB drive), while it will redownload all your PS+ cloud saves usually 100% of stuff isn't kept there, just one save per game.
I traded in my ps4 and bought a new one over the weekend, it was pretty easy and i was back up and running in under an hour. Backup all my saves, insert new drive, have the latest PS4 firmware on thumb drive and install at boot (its 800 megs not 300 meg update firmware), login to PSN, redownload all my games, restore all my saves, and good to go.
keep in mind you can only restore saves for games that are installed, I had saves from games I traded in like infamous, MGS, 1886, etc that I can't restore unless I rebuy and install the games. Don't really care, I'll just copy them all to my dropbox and keep as backup, but something to keep in mind.