Should be quite easy, start inside car at handle end, unclip cable from handle and go from there. remember to take note of where cable runs before removal, and take it slowly step by step.
Welcome to the club, As Stuart said firstly check the wiring to see if anythings obvious.
If not your'e probably going to be best off getting an auto electrician out.
Yes you need remote part as well, this is what you need
http://www.ebay.co.uk/itm/LEXUS-IS200-IS300-GS300-RX300-etc-DENSO-1512V-key-fob-remote-alarm-GREAT-VALUE-/181089597761?pt=UK_Car_Parts_Vehicles_Automobila_ET&hash=item2a29c7f941
The glass can be replaced on it's own, I have an original glass you could have for £12 posted, but does the LE have the photochromatic as well as the heated mirror, like the is300?
320d is a common car mikey Rory was looking for something rare and not too common like a BMW everyone has thier own point of view mikey. Tell anyone you own a Subaru and they automatically think quick fast car. The brand is known for that even though all their cars are not high performance but most associate a Subaru or the badge with high performance so i wont be wrong with that comment . Feel free to copy and paste my sig to yours if you like it soo much to comment about it. Am not the only one here with a list in their sig. Wont fall for the usual trap which will end up in Rorys tread being hijacked and thrown off topic. One advice before i sign off Mikey don't go flexing your 320d's mucles near a Subaru Legacy R if you want to save face.
Can we keep on topic guy's? Please don't turn Rory's thread into a personal slanging match.