Rooting means unlocking full admin control of the tablet. Custom ROMs such CM10 typically come with full admin control (i.e., already "rooted"). Furthermore when installed the custom ROM would replace the stock ROM in whole, hence there is no point in rooting stock ROM if you plan to install CM10 internally.
But in case you'd like to root the stock ROM just to see what it's like to use a rooted NT (I too had done this out of curiosity), I would recommend flashing the update.zip referenced in this post
at XDA by liquidzoo as it's more up to date than the rooting package assembled by Albert Wertz.
Also, Albert's SDNT16or8gbV4.7.zip is not an archive file for installation to emmc but rather contains a Rooting SD card image and the disk image writer program to write the image to SD.