The first thing to do is to go into all instances of iTunes, in preferences/devices and check the box that says "Prevent iphones, ipods and ipads from syncing automatically". Hit OK, etc to make that change stick.
Be careful if you allow it to sync to the mac. Make sure all the content you are getting from the pc is also on the mac, including pictures, content not purchased from itunes and anything not in the cloud.
Take an encrypted backup on the pc first, in case you have to restore. Make sure the backup is encrypted (a checkbox in itunes), so it includes all your network settings, saved passwords, etc. Otherwise it won't include that stuff. You will have to turn off cloud backup to do that for now. You can turn it back on now, but you can still let contacts and everything else sync to the cloud, those are individual settings on the iphone and ipad.
Once you tell it to sync with the mac, it won't sync with the pc anymore. Unless you go back to the PC and tell it to do the sync there. itunes knows where the device is currently syncing.
You can also copy itunes libraries. The steps are consolidate the library, then copy the content over. (search for it, you'll find it.) but it sounds like you already set up a new itunes library on your mac. You can replace it if you want to. Anyway, this is in preferences/advanced on the mac, the location of the library is there and you may want to check the two boxes below that. (depends on how you are storing your movies, if you don't want copies in the itunes library vs just a pointer/entry, then you may not want to check one of them.)
As long as you have an up to date encrypted backup of your iphone and ipad on the PC before you let the mac's itunes sync with them, you should be able to easily go back until you get it right.
Originally Posted by
ant_west
1) Do I need to transfer the iTunes library from my old PC to the MacBook? given the music is in the cloud I'm guessing not. What about the TV series - presumably I can just do a "download purchases" on the MacBook and they would be re-downloaded? For movies I am assuming I would need to re-load them into the MacBook's iTunes library by pointing it at the appropriate folder on the NAS.
If everything is purchased from the itunes store or matched (not everything always gets matched, you have to check) then maybe not? The movies, sure you can re-import them into the new itunes. Or you can just clone the itunes library from the pc and make that your new itunes library on the mac if you do it properly. If you purchased the movies in the itunes store, I think you can just download them again. The itunes library on the mac could even be on the NAS if you want it to be there. For now, don't let it share the same location with the PC, they both have some meta data files they will want to manage individually so they don't share well that way.
If the items show up in iTunes with the cloud icon, you are good. The file doesn't have to be present on the local file system. iTunes will download it when it's needed. Same on the devices. (You can download whatever you want to, ie, if you want to watch a movie or tv show when you don't have a data connection, you'll need to make sure the file is downloaded on the device.)
Good luck.
-David