I'm terribly sorry, I misread the title of the post....
I thought you wanted to replace your Soda Stream head unit...how great would that be?!?!? Select a flavour with the MFSW and press the eject button - out comes an icy cold stream of carbonated beverage....hmmmmm
However I digress...
I have replaced the stock Audi Symphony II+ in my A3 with the Audi Navigation Plus system (RNS-E) and also replaced the RCD300 in my wife's Golf V with an RCD310 (also had to replace the CANbus gateway due to a current leakeage issue) so the principals would be similar.
I am sure someone with direct experience of your upgrade will be more specific but if you are mildly handy you should be able to do it without too much effort.
The theory is:
pull out old HU
run GPS antenna from back of new HU up behind dash to something metal to attach it (its magnetic)
cable in quadlock and aerial, push in new HU.
Unlock new HU using supplied security code.
Then the car will need to be recoded for the new features using VCDS (otherwise known as VAGCOM). Should only take a few hours at most, or for someone experienced it would only take an hour or so.
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