Hi there,
This thread probably does want moving so i'm sure a moderator will be along soon.
Have a search on here for the questions and you'll find a wealth of knowledge!
In short, I can give a bit of basic info though,
Remap - most people recommend Rtech
http://www.r-techpower.co.ukThey're meant to be excellent for maps.
Leather interior - it can be done as far as I know but the interior will be quite pricey as there aren't that many being broken. Keep an eye on the for sale section here.
Radio - if you want to stay OEM you will be wanting an RNS-510 (sat nav) or an RCD-510 (without). You can add bluetooth I believe and the RCD can be bought with DAB.Both are really nice and look a lot better over the standard one. If you fancy it, you can swap your climate controls over for MK6 ones and they display on the radio screen which is a nice touch.
You can also fit the MDI kit in the centre cubby which is the OEM plug in for your phone - play and control music through it :D