Just check the Navtec website here for updates, if the version number there is newer then update.
Easy as piss.... Download file from website, extract, copy to SD card... might wanna take copy of stuff that is already on the SD, then delete it.
Postcode search is easy, not sure why you're struggling so much?

(there was a bit of sarcasm towards VW there)
Tap 'New destination' -> tap the 'city/town' -> tap on bottom left where it says 'PSCD' or 'Pstcd' or something like that... it will then bring up a number pad (as continental postcodes are generally only numbers), tap the 'ABC' on bottom left, enter the 2 letters, tap '123' enter number, tap 'ABC' again to put the last characters....
Not sure why VW can't manage to get the software to start off with letters when the country is set to England, Wales, Scotland and Ireland.