Reply to Using S4 Library ITunes etc

Sorry if this has been asked before - but its something thats ruining my life and S4 - im having a bit of a mare getting to grips with the s4 and wondered if somebody could point me in the right direction.

I bought the s4 last year and have so far never really used it.

I have a Xone DX running Serato itch and like the way i can just drag stuff from my external hdd into the crates. This doesnt seem to quite work the same way with traktor pro 2 and i find that the browsing files experience not to be as easy.

After viewing the s4 tutorial which i bought from DJTT - Iain VERY breifyly tells you how to get the tunes in from itunes - but that was it.

Now i dont really ever use itunes (except fpor managing my Ipad (i dont have more than 20 or so tracks on that) - and after a bit of messing around with trying to import manually and getting frustrated on finding stuff - i decided to bite the bullet and install itunes on my laptop after reading various community s saying that the S4 is best organised with Itunes.

I have 3 apple devices:
Ipad , Iphone & Ipod 80gb (old colour - not touch)
I have 2 PCs - Laptop for Music (DJing) and Main Workstation for Music Production and general Work. Itunes is now installed on both.
The Ipad and Iphone are connected to the main workstation.

On the Laptop i only use the colour ipod in relation to DJing - I also have a Samsung 500GB Hard drive for all my music to take pressure off the internal Laptop hDD.
When add a folder to itunes on the Laptop - from the Samsung HDD- could somebody tell me - does that then copy the file/folder to the Laptop internal hdd and play from there?

I want it to play from the EXTERNAL hdd - not the internal one. If it does copy to and play from the INTERNAL HDD how can i change this please?
I only have music on the INTERNAL HDD for backup purposed should the EXTERNAL hdd fail.

Also i would ideally like to be able to sit down at my main workstation to organise the music and playlists - not the laptop - is this somehow possible - bearing in mind the multiple devices and installations of iTunes on more than one computer?

Also - i dont want to sync the DJ Music with anything else other than my little ipod. In other word i dont want itunes to add / remove from my other 2 devices.

I have 10000+ tunes i have collected over the years and a lot of vynil rips i spent many hours doing - all these are present in Serato but does this mean im going to have to spend days getting this lot into Traktor?
Currently they are not in iTunes.

Any advice would be greatly appreciated - the thick layer of dust on the S4 is a testament to how much this has stopped me thus far enjoying my purchase of months and months ago and i don't dare even believe about playing out with it.